1 /*
2 *
3 * Copyright 2017 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19 #include <grpc/support/port_platform.h>
20
21 #include "src/core/lib/iomgr/port.h"
22
23 #include <grpc/support/log.h>
24
25 /* This polling engine is only relevant on linux kernels supporting epoll() */
26 #ifdef GRPC_LINUX_EPOLL_CREATE1
27
28 #include "src/core/lib/iomgr/ev_epollex_linux.h"
29
30 #include <assert.h>
31 #include <errno.h>
32 #include <limits.h>
33 #include <poll.h>
34 #include <pthread.h>
35 #include <string.h>
36 #include <sys/epoll.h>
37 #include <sys/socket.h>
38 #include <sys/syscall.h>
39 #include <unistd.h>
40
41 #include <grpc/support/alloc.h>
42 #include <grpc/support/string_util.h>
43
44 #include "absl/container/inlined_vector.h"
45 #include "src/core/lib/debug/stats.h"
46 #include "src/core/lib/gpr/spinlock.h"
47 #include "src/core/lib/gpr/tls.h"
48 #include "src/core/lib/gpr/useful.h"
49 #include "src/core/lib/gprpp/manual_constructor.h"
50 #include "src/core/lib/gprpp/ref_counted.h"
51 #include "src/core/lib/gprpp/sync.h"
52 #include "src/core/lib/iomgr/block_annotate.h"
53 #include "src/core/lib/iomgr/iomgr_internal.h"
54 #include "src/core/lib/iomgr/is_epollexclusive_available.h"
55 #include "src/core/lib/iomgr/lockfree_event.h"
56 #include "src/core/lib/iomgr/sys_epoll_wrapper.h"
57 #include "src/core/lib/iomgr/timer.h"
58 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
59 #include "src/core/lib/profiling/timers.h"
60
61 // debug aid: create workers on the heap (allows asan to spot
62 // use-after-destruction)
63 //#define GRPC_EPOLLEX_CREATE_WORKERS_ON_HEAP 1
64
65 #define MAX_EPOLL_EVENTS 100
66 // TODO(juanlishen): We use a greater-than-one value here as a workaround fix to
67 // a keepalive ping timeout issue. We may want to revert https://github
68 // .com/grpc/grpc/pull/14943 once we figure out the root cause.
69 #define MAX_EPOLL_EVENTS_HANDLED_EACH_POLL_CALL 16
70 #define MAX_FDS_IN_CACHE 32
71
72 grpc_core::DebugOnlyTraceFlag grpc_trace_pollable_refcount(false,
73 "pollable_refcount");
74
75 /*******************************************************************************
76 * pollable Declarations
77 */
78
79 typedef enum { PO_MULTI, PO_FD, PO_EMPTY } pollable_type;
80
81 typedef struct pollable pollable;
82
83 /// A pollable is something that can be polled: it has an epoll set to poll on,
84 /// and a wakeup fd for kicks
85 /// There are three broad types:
86 /// - PO_EMPTY - the empty pollable, used before file descriptors are added to
87 /// a pollset
88 /// - PO_FD - a pollable containing only one FD - used to optimize single-fd
89 /// pollsets (which are common with synchronous api usage)
90 /// - PO_MULTI - a pollable containing many fds
91 struct pollable {
92 pollable_type type; // immutable
93 grpc_core::RefCount refs;
94
95 int epfd;
96 grpc_wakeup_fd wakeup;
97
98 // The following are relevant only for type PO_FD
99 grpc_fd* owner_fd; // Set to the owner_fd if the type is PO_FD
100 gpr_mu owner_orphan_mu; // Synchronizes access to owner_orphaned field
101 bool owner_orphaned; // Is the owner fd orphaned
102
103 grpc_pollset_set* pollset_set;
104 pollable* next;
105 pollable* prev;
106
107 gpr_mu mu;
108 grpc_pollset_worker* root_worker;
109
110 int event_cursor;
111 int event_count;
112 struct epoll_event events[MAX_EPOLL_EVENTS];
113 };
114
pollable_type_string(pollable_type t)115 static const char* pollable_type_string(pollable_type t) {
116 switch (t) {
117 case PO_MULTI:
118 return "pollset";
119 case PO_FD:
120 return "fd";
121 case PO_EMPTY:
122 return "empty";
123 }
124 return "<invalid>";
125 }
126
pollable_desc(pollable * p)127 static char* pollable_desc(pollable* p) {
128 char* out;
129 gpr_asprintf(&out, "type=%s epfd=%d wakeup=%d", pollable_type_string(p->type),
130 p->epfd, p->wakeup.read_fd);
131 return out;
132 }
133
134 /// Shared empty pollable - used by pollset to poll on until the first fd is
135 /// added
136 static pollable* g_empty_pollable;
137
138 static grpc_error* pollable_create(pollable_type type, pollable** p);
pollable_ref(pollable * p,const grpc_core::DebugLocation & dbg_loc,const char * reason)139 static pollable* pollable_ref(pollable* p,
140 const grpc_core::DebugLocation& dbg_loc,
141 const char* reason) {
142 p->refs.Ref(dbg_loc, reason);
143 return p;
144 }
pollable_unref(pollable * p,const grpc_core::DebugLocation & dbg_loc,const char * reason)145 static void pollable_unref(pollable* p, const grpc_core::DebugLocation& dbg_loc,
146 const char* reason) {
147 if (p == nullptr) return;
148 if (GPR_UNLIKELY(p != nullptr && p->refs.Unref(dbg_loc, reason))) {
149 GRPC_FD_TRACE("pollable_unref: Closing epfd: %d", p->epfd);
150 close(p->epfd);
151 grpc_wakeup_fd_destroy(&p->wakeup);
152 gpr_mu_destroy(&p->owner_orphan_mu);
153 gpr_mu_destroy(&p->mu);
154 gpr_free(p);
155 }
156 }
157 #define POLLABLE_REF(p, r) pollable_ref((p), DEBUG_LOCATION, (r))
158 #define POLLABLE_UNREF(p, r) pollable_unref((p), DEBUG_LOCATION, (r))
159
160 /*******************************************************************************
161 * Fd Declarations
162 */
163
164 struct grpc_fd {
grpc_fdgrpc_fd165 grpc_fd(int fd, const char* name, bool track_err)
166 : fd(fd), track_err(track_err) {
167 gpr_mu_init(&orphan_mu);
168 gpr_mu_init(&pollable_mu);
169 read_closure.InitEvent();
170 write_closure.InitEvent();
171 error_closure.InitEvent();
172
173 char* fd_name;
174 gpr_asprintf(&fd_name, "%s fd=%d", name, fd);
175 grpc_iomgr_register_object(&iomgr_object, fd_name);
176 #ifndef NDEBUG
177 if (GRPC_TRACE_FLAG_ENABLED(grpc_trace_fd_refcount)) {
178 gpr_log(GPR_DEBUG, "FD %d %p create %s", fd, this, fd_name);
179 }
180 #endif
181 gpr_free(fd_name);
182 }
183
184 // This is really the dtor, but the poller threads waking up from
185 // epoll_wait() may access the (read|write|error)_closure after destruction.
186 // Since the object will be added to the free pool, this behavior is
187 // not going to cause issues, except spurious events if the FD is reused
188 // while the race happens.
destroygrpc_fd189 void destroy() {
190 grpc_iomgr_unregister_object(&iomgr_object);
191
192 POLLABLE_UNREF(pollable_obj, "fd_pollable");
193
194 // To clear out the allocations of pollset_fds, we need to swap its
195 // contents with a newly-constructed (and soon to be destructed) local
196 // variable of its same type. This is because InlinedVector::clear is _not_
197 // guaranteed to actually free up allocations and this is important since
198 // this object doesn't have a conventional destructor.
199 absl::InlinedVector<int, 1> pollset_fds_tmp;
200 pollset_fds_tmp.swap(pollset_fds);
201
202 gpr_mu_destroy(&pollable_mu);
203 gpr_mu_destroy(&orphan_mu);
204
205 read_closure.DestroyEvent();
206 write_closure.DestroyEvent();
207 error_closure.DestroyEvent();
208
209 invalidate();
210 }
211
212 #ifndef NDEBUG
213 /* Since an fd is never really destroyed (i.e gpr_free() is not called), it is
214 * hard-to-debug cases where fd fields are accessed even after calling
215 * fd_destroy(). The following invalidates fd fields to make catching such
216 * errors easier */
invalidategrpc_fd217 void invalidate() {
218 fd = -1;
219 gpr_atm_no_barrier_store(&refst, -1);
220 memset(&orphan_mu, -1, sizeof(orphan_mu));
221 memset(&pollable_mu, -1, sizeof(pollable_mu));
222 pollable_obj = nullptr;
223 on_done_closure = nullptr;
224 memset(&iomgr_object, -1, sizeof(iomgr_object));
225 track_err = false;
226 }
227 #else
invalidategrpc_fd228 void invalidate() {}
229 #endif
230
231 int fd;
232
233 // refst format:
234 // bit 0 : 1=Active / 0=Orphaned
235 // bits 1-n : refcount
236 // Ref/Unref by two to avoid altering the orphaned bit
237 gpr_atm refst = 1;
238
239 gpr_mu orphan_mu;
240
241 // Protects pollable_obj and pollset_fds.
242 gpr_mu pollable_mu;
243 absl::InlinedVector<int, 1> pollset_fds; // Used in PO_MULTI.
244 pollable* pollable_obj = nullptr; // Used in PO_FD.
245
246 grpc_core::LockfreeEvent read_closure;
247 grpc_core::LockfreeEvent write_closure;
248 grpc_core::LockfreeEvent error_closure;
249
250 struct grpc_fd* freelist_next = nullptr;
251 grpc_closure* on_done_closure = nullptr;
252
253 grpc_iomgr_object iomgr_object;
254
255 // Do we need to track EPOLLERR events separately?
256 bool track_err;
257 };
258
259 static void fd_global_init(void);
260 static void fd_global_shutdown(void);
261
262 /*******************************************************************************
263 * Pollset Declarations
264 */
265
266 struct pwlink {
267 grpc_pollset_worker* next;
268 grpc_pollset_worker* prev;
269 };
270 typedef enum { PWLINK_POLLABLE = 0, PWLINK_POLLSET, PWLINK_COUNT } pwlinks;
271
272 struct grpc_pollset_worker {
273 bool kicked;
274 bool initialized_cv;
275 #ifndef NDEBUG
276 // debug aid: which thread started this worker
277 pid_t originator;
278 #endif
279 gpr_cv cv;
280 grpc_pollset* pollset;
281 pollable* pollable_obj;
282
283 pwlink links[PWLINK_COUNT];
284 };
285
286 struct grpc_pollset {
287 gpr_mu mu;
288 gpr_atm worker_count;
289 gpr_atm active_pollable_type;
290 pollable* active_pollable;
291 bool kicked_without_poller;
292 grpc_closure* shutdown_closure;
293 bool already_shutdown;
294 grpc_pollset_worker* root_worker;
295 int containing_pollset_set_count;
296 };
297
298 /*******************************************************************************
299 * Pollset-set Declarations
300 */
301
302 struct grpc_pollset_set {
303 grpc_core::RefCount refs;
304 gpr_mu mu;
305 grpc_pollset_set* parent;
306
307 size_t pollset_count;
308 size_t pollset_capacity;
309 grpc_pollset** pollsets;
310
311 size_t fd_count;
312 size_t fd_capacity;
313 grpc_fd** fds;
314 };
315
316 /*******************************************************************************
317 * Common helpers
318 */
319
append_error(grpc_error ** composite,grpc_error * error,const char * desc)320 static bool append_error(grpc_error** composite, grpc_error* error,
321 const char* desc) {
322 if (error == GRPC_ERROR_NONE) return true;
323 if (*composite == GRPC_ERROR_NONE) {
324 *composite = GRPC_ERROR_CREATE_FROM_COPIED_STRING(desc);
325 }
326 *composite = grpc_error_add_child(*composite, error);
327 return false;
328 }
329
330 /*******************************************************************************
331 * Fd Definitions
332 */
333
334 /* We need to keep a freelist not because of any concerns of malloc performance
335 * but instead so that implementations with multiple threads in (for example)
336 * epoll_wait deal with the race between pollset removal and incoming poll
337 * notifications.
338 *
339 * The problem is that the poller ultimately holds a reference to this
340 * object, so it is very difficult to know when is safe to free it, at least
341 * without some expensive synchronization.
342 *
343 * If we keep the object freelisted, in the worst case losing this race just
344 * becomes a spurious read notification on a reused fd.
345 */
346
347 static grpc_fd* fd_freelist = nullptr;
348 static gpr_mu fd_freelist_mu;
349
350 #ifndef NDEBUG
351 #define REF_BY(fd, n, reason) ref_by(fd, n, reason, __FILE__, __LINE__)
352 #define UNREF_BY(fd, n, reason) unref_by(fd, n, reason, __FILE__, __LINE__)
ref_by(grpc_fd * fd,int n,const char * reason,const char * file,int line)353 static void ref_by(grpc_fd* fd, int n, const char* reason, const char* file,
354 int line) {
355 if (GRPC_TRACE_FLAG_ENABLED(grpc_trace_fd_refcount)) {
356 gpr_log(GPR_DEBUG,
357 "FD %d %p ref %d %" PRIdPTR " -> %" PRIdPTR " [%s; %s:%d]",
358 fd->fd, fd, n, gpr_atm_no_barrier_load(&fd->refst),
359 gpr_atm_no_barrier_load(&fd->refst) + n, reason, file, line);
360 }
361 #else
362 #define REF_BY(fd, n, reason) \
363 do { \
364 ref_by(fd, n); \
365 (void)(reason); \
366 } while (0)
367 #define UNREF_BY(fd, n, reason) \
368 do { \
369 unref_by(fd, n); \
370 (void)(reason); \
371 } while (0)
372 static void ref_by(grpc_fd* fd, int n) {
373 #endif
374 GPR_ASSERT(gpr_atm_no_barrier_fetch_add(&fd->refst, n) > 0);
375 }
376
377 /* Uninitialize and add to the freelist */
378 static void fd_destroy(void* arg, grpc_error* /*error*/) {
379 grpc_fd* fd = static_cast<grpc_fd*>(arg);
380 fd->destroy();
381
382 /* Add the fd to the freelist */
383 gpr_mu_lock(&fd_freelist_mu);
384 fd->freelist_next = fd_freelist;
385 fd_freelist = fd;
386 gpr_mu_unlock(&fd_freelist_mu);
387 }
388
389 #ifndef NDEBUG
390 static void unref_by(grpc_fd* fd, int n, const char* reason, const char* file,
391 int line) {
392 if (GRPC_TRACE_FLAG_ENABLED(grpc_trace_fd_refcount)) {
393 gpr_log(GPR_DEBUG,
394 "FD %d %p unref %d %" PRIdPTR " -> %" PRIdPTR " [%s; %s:%d]",
395 fd->fd, fd, n, gpr_atm_no_barrier_load(&fd->refst),
396 gpr_atm_no_barrier_load(&fd->refst) - n, reason, file, line);
397 }
398 #else
399 static void unref_by(grpc_fd* fd, int n) {
400 #endif
401 gpr_atm old = gpr_atm_full_fetch_add(&fd->refst, -n);
402 if (old == n) {
403 grpc_core::ExecCtx::Run(
404 DEBUG_LOCATION,
405 GRPC_CLOSURE_CREATE(fd_destroy, fd, grpc_schedule_on_exec_ctx),
406 GRPC_ERROR_NONE);
407 } else {
408 GPR_ASSERT(old > n);
409 }
410 }
411
412 static void fd_global_init(void) { gpr_mu_init(&fd_freelist_mu); }
413
414 static void fd_global_shutdown(void) {
415 // TODO(guantaol): We don't have a reasonable explanation about this
416 // lock()/unlock() pattern. It can be a valid barrier if there is at most one
417 // pending lock() at this point. Otherwise, there is still a possibility of
418 // use-after-free race. Need to reason about the code and/or clean it up.
419 gpr_mu_lock(&fd_freelist_mu);
420 gpr_mu_unlock(&fd_freelist_mu);
421 while (fd_freelist != nullptr) {
422 grpc_fd* fd = fd_freelist;
423 fd_freelist = fd_freelist->freelist_next;
424 gpr_free(fd);
425 }
426 gpr_mu_destroy(&fd_freelist_mu);
427 }
428
429 static grpc_fd* fd_create(int fd, const char* name, bool track_err) {
430 grpc_fd* new_fd = nullptr;
431
432 gpr_mu_lock(&fd_freelist_mu);
433 if (fd_freelist != nullptr) {
434 new_fd = fd_freelist;
435 fd_freelist = fd_freelist->freelist_next;
436 }
437 gpr_mu_unlock(&fd_freelist_mu);
438
439 if (new_fd == nullptr) {
440 new_fd = static_cast<grpc_fd*>(gpr_malloc(sizeof(grpc_fd)));
441 }
442
443 return new (new_fd) grpc_fd(fd, name, track_err);
444 }
445
446 static int fd_wrapped_fd(grpc_fd* fd) {
447 int ret_fd = fd->fd;
448 return (gpr_atm_acq_load(&fd->refst) & 1) ? ret_fd : -1;
449 }
450
451 static void fd_orphan(grpc_fd* fd, grpc_closure* on_done, int* release_fd,
452 const char* reason) {
453 bool is_fd_closed = false;
454
455 gpr_mu_lock(&fd->orphan_mu);
456
457 // Get the fd->pollable_obj and set the owner_orphaned on that pollable to
458 // true so that the pollable will no longer access its owner_fd field.
459 gpr_mu_lock(&fd->pollable_mu);
460 pollable* pollable_obj = fd->pollable_obj;
461
462 if (pollable_obj) {
463 gpr_mu_lock(&pollable_obj->owner_orphan_mu);
464 pollable_obj->owner_orphaned = true;
465 }
466
467 fd->on_done_closure = on_done;
468
469 /* If release_fd is not NULL, we should be relinquishing control of the file
470 descriptor fd->fd (but we still own the grpc_fd structure). */
471 if (release_fd != nullptr) {
472 // Remove the FD from all epolls sets, before releasing it.
473 // Otherwise, we will receive epoll events after we release the FD.
474 epoll_event ev_fd;
475 memset(&ev_fd, 0, sizeof(ev_fd));
476 if (pollable_obj != nullptr) { // For PO_FD.
477 epoll_ctl(pollable_obj->epfd, EPOLL_CTL_DEL, fd->fd, &ev_fd);
478 }
479 for (size_t i = 0; i < fd->pollset_fds.size(); ++i) { // For PO_MULTI.
480 const int epfd = fd->pollset_fds[i];
481 epoll_ctl(epfd, EPOLL_CTL_DEL, fd->fd, &ev_fd);
482 }
483 *release_fd = fd->fd;
484 } else {
485 close(fd->fd);
486 is_fd_closed = true;
487 }
488
489 // TODO(sreek): handle fd removal (where is_fd_closed=false)
490 if (!is_fd_closed) {
491 GRPC_FD_TRACE("epoll_fd %p (%d) was orphaned but not closed.", fd, fd->fd);
492 }
493
494 /* Remove the active status but keep referenced. We want this grpc_fd struct
495 to be alive (and not added to freelist) until the end of this function */
496 REF_BY(fd, 1, reason);
497
498 grpc_core::ExecCtx::Run(DEBUG_LOCATION, fd->on_done_closure, GRPC_ERROR_NONE);
499
500 if (pollable_obj) {
501 gpr_mu_unlock(&pollable_obj->owner_orphan_mu);
502 }
503
504 gpr_mu_unlock(&fd->pollable_mu);
505 gpr_mu_unlock(&fd->orphan_mu);
506
507 UNREF_BY(fd, 2, reason); /* Drop the reference */
508 }
509
510 static bool fd_is_shutdown(grpc_fd* fd) {
511 return fd->read_closure.IsShutdown();
512 }
513
514 /* Might be called multiple times */
515 static void fd_shutdown(grpc_fd* fd, grpc_error* why) {
516 if (fd->read_closure.SetShutdown(GRPC_ERROR_REF(why))) {
517 if (shutdown(fd->fd, SHUT_RDWR)) {
518 if (errno != ENOTCONN) {
519 gpr_log(GPR_ERROR, "Error shutting down fd %d. errno: %d",
520 grpc_fd_wrapped_fd(fd), errno);
521 }
522 }
523 fd->write_closure.SetShutdown(GRPC_ERROR_REF(why));
524 fd->error_closure.SetShutdown(GRPC_ERROR_REF(why));
525 }
526 GRPC_ERROR_UNREF(why);
527 }
528
529 static void fd_notify_on_read(grpc_fd* fd, grpc_closure* closure) {
530 fd->read_closure.NotifyOn(closure);
531 }
532
533 static void fd_notify_on_write(grpc_fd* fd, grpc_closure* closure) {
534 fd->write_closure.NotifyOn(closure);
535 }
536
537 static void fd_notify_on_error(grpc_fd* fd, grpc_closure* closure) {
538 fd->error_closure.NotifyOn(closure);
539 }
540
541 static bool fd_has_pollset(grpc_fd* fd, grpc_pollset* pollset) {
542 const int epfd = pollset->active_pollable->epfd;
543 grpc_core::MutexLock lock(&fd->pollable_mu);
544 for (size_t i = 0; i < fd->pollset_fds.size(); ++i) {
545 if (fd->pollset_fds[i] == epfd) {
546 return true;
547 }
548 }
549 return false;
550 }
551
552 static void fd_add_pollset(grpc_fd* fd, grpc_pollset* pollset) {
553 const int epfd = pollset->active_pollable->epfd;
554 grpc_core::MutexLock lock(&fd->pollable_mu);
555 fd->pollset_fds.push_back(epfd);
556 }
557
558 /*******************************************************************************
559 * Pollable Definitions
560 */
561
562 static grpc_error* pollable_create(pollable_type type, pollable** p) {
563 *p = nullptr;
564
565 int epfd = epoll_create1(EPOLL_CLOEXEC);
566 if (epfd == -1) {
567 return GRPC_OS_ERROR(errno, "epoll_create1");
568 }
569 GRPC_FD_TRACE("Pollable_create: created epfd: %d (type: %d)", epfd, type);
570 *p = static_cast<pollable*>(gpr_malloc(sizeof(**p)));
571 grpc_error* err = grpc_wakeup_fd_init(&(*p)->wakeup);
572 if (err != GRPC_ERROR_NONE) {
573 GRPC_FD_TRACE(
574 "Pollable_create: closed epfd: %d (type: %d). wakeupfd_init error",
575 epfd, type);
576 close(epfd);
577 gpr_free(*p);
578 *p = nullptr;
579 return err;
580 }
581 struct epoll_event ev;
582 ev.events = static_cast<uint32_t>(EPOLLIN | EPOLLET);
583 ev.data.ptr = (void*)(1 | (intptr_t) & (*p)->wakeup);
584 if (epoll_ctl(epfd, EPOLL_CTL_ADD, (*p)->wakeup.read_fd, &ev) != 0) {
585 err = GRPC_OS_ERROR(errno, "epoll_ctl");
586 GRPC_FD_TRACE(
587 "Pollable_create: closed epfd: %d (type: %d). epoll_ctl error", epfd,
588 type);
589 close(epfd);
590 grpc_wakeup_fd_destroy(&(*p)->wakeup);
591 gpr_free(*p);
592 *p = nullptr;
593 return err;
594 }
595
596 (*p)->type = type;
597 new (&(*p)->refs) grpc_core::RefCount(1, &grpc_trace_pollable_refcount);
598 gpr_mu_init(&(*p)->mu);
599 (*p)->epfd = epfd;
600 (*p)->owner_fd = nullptr;
601 gpr_mu_init(&(*p)->owner_orphan_mu);
602 (*p)->owner_orphaned = false;
603 (*p)->pollset_set = nullptr;
604 (*p)->next = (*p)->prev = *p;
605 (*p)->root_worker = nullptr;
606 (*p)->event_cursor = 0;
607 (*p)->event_count = 0;
608 return GRPC_ERROR_NONE;
609 }
610
611 static grpc_error* pollable_add_fd(pollable* p, grpc_fd* fd) {
612 grpc_error* error = GRPC_ERROR_NONE;
613 static const char* err_desc = "pollable_add_fd";
614 const int epfd = p->epfd;
615 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
616 gpr_log(GPR_INFO, "add fd %p (%d) to pollable %p", fd, fd->fd, p);
617 }
618
619 struct epoll_event ev_fd;
620 ev_fd.events =
621 static_cast<uint32_t>(EPOLLET | EPOLLIN | EPOLLOUT | EPOLLEXCLUSIVE);
622 /* Use the second least significant bit of ev_fd.data.ptr to store track_err
623 * to avoid synchronization issues when accessing it after receiving an event.
624 * Accessing fd would be a data race there because the fd might have been
625 * returned to the free list at that point. */
626 ev_fd.data.ptr = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(fd) |
627 (fd->track_err ? 2 : 0));
628 GRPC_STATS_INC_SYSCALL_EPOLL_CTL();
629 if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd->fd, &ev_fd) != 0) {
630 switch (errno) {
631 case EEXIST:
632 break;
633 default:
634 append_error(&error, GRPC_OS_ERROR(errno, "epoll_ctl"), err_desc);
635 }
636 }
637
638 return error;
639 }
640
641 /*******************************************************************************
642 * Pollset Definitions
643 */
644
645 GPR_TLS_DECL(g_current_thread_pollset);
646 GPR_TLS_DECL(g_current_thread_worker);
647
648 /* Global state management */
649 static grpc_error* pollset_global_init(void) {
650 gpr_tls_init(&g_current_thread_pollset);
651 gpr_tls_init(&g_current_thread_worker);
652 return pollable_create(PO_EMPTY, &g_empty_pollable);
653 }
654
655 static void pollset_global_shutdown(void) {
656 POLLABLE_UNREF(g_empty_pollable, "g_empty_pollable");
657 gpr_tls_destroy(&g_current_thread_pollset);
658 gpr_tls_destroy(&g_current_thread_worker);
659 }
660
661 /* pollset->mu must be held while calling this function */
662 static void pollset_maybe_finish_shutdown(grpc_pollset* pollset) {
663 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
664 gpr_log(GPR_INFO,
665 "PS:%p (pollable:%p) maybe_finish_shutdown sc=%p (target:!NULL) "
666 "rw=%p (target:NULL) cpsc=%d (target:0)",
667 pollset, pollset->active_pollable, pollset->shutdown_closure,
668 pollset->root_worker, pollset->containing_pollset_set_count);
669 }
670 if (pollset->shutdown_closure != nullptr && pollset->root_worker == nullptr &&
671 pollset->containing_pollset_set_count == 0) {
672 GPR_TIMER_MARK("pollset_finish_shutdown", 0);
673 grpc_core::ExecCtx::Run(DEBUG_LOCATION, pollset->shutdown_closure,
674 GRPC_ERROR_NONE);
675 pollset->shutdown_closure = nullptr;
676 pollset->already_shutdown = true;
677 }
678 }
679
680 /* pollset->mu must be held before calling this function,
681 * pollset->active_pollable->mu & specific_worker->pollable_obj->mu must not be
682 * held */
683 static grpc_error* kick_one_worker(grpc_pollset_worker* specific_worker) {
684 GPR_TIMER_SCOPE("kick_one_worker", 0);
685 pollable* p = specific_worker->pollable_obj;
686 grpc_core::MutexLock lock(&p->mu);
687 GPR_ASSERT(specific_worker != nullptr);
688 if (specific_worker->kicked) {
689 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
690 gpr_log(GPR_INFO, "PS:%p kicked_specific_but_already_kicked", p);
691 }
692 GRPC_STATS_INC_POLLSET_KICKED_AGAIN();
693 return GRPC_ERROR_NONE;
694 }
695 if (gpr_tls_get(&g_current_thread_worker) == (intptr_t)specific_worker) {
696 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
697 gpr_log(GPR_INFO, "PS:%p kicked_specific_but_awake", p);
698 }
699 GRPC_STATS_INC_POLLSET_KICK_OWN_THREAD();
700 specific_worker->kicked = true;
701 return GRPC_ERROR_NONE;
702 }
703 if (specific_worker == p->root_worker) {
704 GRPC_STATS_INC_POLLSET_KICK_WAKEUP_FD();
705 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
706 gpr_log(GPR_INFO, "PS:%p kicked_specific_via_wakeup_fd", p);
707 }
708 specific_worker->kicked = true;
709 grpc_error* error = grpc_wakeup_fd_wakeup(&p->wakeup);
710 return error;
711 }
712 if (specific_worker->initialized_cv) {
713 GRPC_STATS_INC_POLLSET_KICK_WAKEUP_CV();
714 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
715 gpr_log(GPR_INFO, "PS:%p kicked_specific_via_cv", p);
716 }
717 specific_worker->kicked = true;
718 gpr_cv_signal(&specific_worker->cv);
719 return GRPC_ERROR_NONE;
720 }
721 // we can get here during end_worker after removing specific_worker from the
722 // pollable list but before removing it from the pollset list
723 return GRPC_ERROR_NONE;
724 }
725
726 static grpc_error* pollset_kick(grpc_pollset* pollset,
727 grpc_pollset_worker* specific_worker) {
728 GPR_TIMER_SCOPE("pollset_kick", 0);
729 GRPC_STATS_INC_POLLSET_KICK();
730 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
731 gpr_log(GPR_INFO,
732 "PS:%p kick %p tls_pollset=%p tls_worker=%p pollset.root_worker=%p",
733 pollset, specific_worker,
734 (void*)gpr_tls_get(&g_current_thread_pollset),
735 (void*)gpr_tls_get(&g_current_thread_worker), pollset->root_worker);
736 }
737 if (specific_worker == nullptr) {
738 if (gpr_tls_get(&g_current_thread_pollset) != (intptr_t)pollset) {
739 if (pollset->root_worker == nullptr) {
740 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
741 gpr_log(GPR_INFO, "PS:%p kicked_any_without_poller", pollset);
742 }
743 GRPC_STATS_INC_POLLSET_KICKED_WITHOUT_POLLER();
744 pollset->kicked_without_poller = true;
745 return GRPC_ERROR_NONE;
746 } else {
747 // We've been asked to kick a poller, but we haven't been told which one
748 // ... any will do
749 // We look at the pollset worker list because:
750 // 1. the pollable list may include workers from other pollers, so we'd
751 // need to do an O(N) search
752 // 2. we'd additionally need to take the pollable lock, which we've so
753 // far avoided
754 // Now, we would prefer to wake a poller in cv_wait, and not in
755 // epoll_wait (since the latter would imply the need to do an additional
756 // wakeup)
757 // We know that if a worker is at the root of a pollable, it's (likely)
758 // also the root of a pollset, and we know that if a worker is NOT at
759 // the root of a pollset, it's (likely) not at the root of a pollable,
760 // so we take our chances and choose the SECOND worker enqueued against
761 // the pollset as a worker that's likely to be in cv_wait
762 return kick_one_worker(
763 pollset->root_worker->links[PWLINK_POLLSET].next);
764 }
765 } else {
766 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
767 gpr_log(GPR_INFO, "PS:%p kicked_any_but_awake", pollset);
768 }
769 GRPC_STATS_INC_POLLSET_KICK_OWN_THREAD();
770 return GRPC_ERROR_NONE;
771 }
772 } else {
773 return kick_one_worker(specific_worker);
774 }
775 }
776
777 static grpc_error* pollset_kick_all(grpc_pollset* pollset) {
778 GPR_TIMER_SCOPE("pollset_kick_all", 0);
779 grpc_error* error = GRPC_ERROR_NONE;
780 const char* err_desc = "pollset_kick_all";
781 grpc_pollset_worker* w = pollset->root_worker;
782 if (w != nullptr) {
783 do {
784 GRPC_STATS_INC_POLLSET_KICK();
785 append_error(&error, kick_one_worker(w), err_desc);
786 w = w->links[PWLINK_POLLSET].next;
787 } while (w != pollset->root_worker);
788 }
789 return error;
790 }
791
792 static void pollset_init(grpc_pollset* pollset, gpr_mu** mu) {
793 gpr_mu_init(&pollset->mu);
794 gpr_atm_no_barrier_store(&pollset->worker_count, 0);
795 gpr_atm_no_barrier_store(&pollset->active_pollable_type, PO_EMPTY);
796 pollset->active_pollable = POLLABLE_REF(g_empty_pollable, "pollset");
797 pollset->kicked_without_poller = false;
798 pollset->shutdown_closure = nullptr;
799 pollset->already_shutdown = false;
800 pollset->root_worker = nullptr;
801 pollset->containing_pollset_set_count = 0;
802 *mu = &pollset->mu;
803 }
804
805 static int poll_deadline_to_millis_timeout(grpc_millis millis) {
806 if (millis == GRPC_MILLIS_INF_FUTURE) return -1;
807 grpc_millis delta = millis - grpc_core::ExecCtx::Get()->Now();
808 if (delta > INT_MAX)
809 return INT_MAX;
810 else if (delta < 0)
811 return 0;
812 else
813 return static_cast<int>(delta);
814 }
815
816 static void fd_become_readable(grpc_fd* fd) { fd->read_closure.SetReady(); }
817
818 static void fd_become_writable(grpc_fd* fd) { fd->write_closure.SetReady(); }
819
820 static void fd_has_errors(grpc_fd* fd) { fd->error_closure.SetReady(); }
821
822 /* Get the pollable_obj attached to this fd. If none is attached, create a new
823 * pollable object (of type PO_FD), attach it to the fd and return it
824 *
825 * Note that if a pollable object is already attached to the fd, it may be of
826 * either PO_FD or PO_MULTI type */
827 static grpc_error* get_fd_pollable(grpc_fd* fd, pollable** p) {
828 gpr_mu_lock(&fd->pollable_mu);
829 grpc_error* error = GRPC_ERROR_NONE;
830 static const char* err_desc = "get_fd_pollable";
831 if (fd->pollable_obj == nullptr) {
832 if (append_error(&error, pollable_create(PO_FD, &fd->pollable_obj),
833 err_desc)) {
834 fd->pollable_obj->owner_fd = fd;
835 if (!append_error(&error, pollable_add_fd(fd->pollable_obj, fd),
836 err_desc)) {
837 POLLABLE_UNREF(fd->pollable_obj, "fd_pollable");
838 fd->pollable_obj = nullptr;
839 }
840 }
841 }
842 if (error == GRPC_ERROR_NONE) {
843 GPR_ASSERT(fd->pollable_obj != nullptr);
844 *p = POLLABLE_REF(fd->pollable_obj, "pollset");
845 } else {
846 GPR_ASSERT(fd->pollable_obj == nullptr);
847 *p = nullptr;
848 }
849 gpr_mu_unlock(&fd->pollable_mu);
850 return error;
851 }
852
853 /* pollset->po.mu lock must be held by the caller before calling this */
854 static void pollset_shutdown(grpc_pollset* pollset, grpc_closure* closure) {
855 GPR_TIMER_SCOPE("pollset_shutdown", 0);
856 GPR_ASSERT(pollset->shutdown_closure == nullptr);
857 pollset->shutdown_closure = closure;
858 GRPC_LOG_IF_ERROR("pollset_shutdown", pollset_kick_all(pollset));
859 pollset_maybe_finish_shutdown(pollset);
860 }
861
862 static grpc_error* pollable_process_events(grpc_pollset* pollset,
863 pollable* pollable_obj, bool drain) {
864 GPR_TIMER_SCOPE("pollable_process_events", 0);
865 static const char* err_desc = "pollset_process_events";
866 // Use a simple heuristic to determine how many fd events to process
867 // per loop iteration. (events/workers)
868 int handle_count = 1;
869 int worker_count = gpr_atm_no_barrier_load(&pollset->worker_count);
870 GPR_ASSERT(worker_count > 0);
871 handle_count =
872 (pollable_obj->event_count - pollable_obj->event_cursor) / worker_count;
873 if (handle_count == 0) {
874 handle_count = 1;
875 } else if (handle_count > MAX_EPOLL_EVENTS_HANDLED_EACH_POLL_CALL) {
876 handle_count = MAX_EPOLL_EVENTS_HANDLED_EACH_POLL_CALL;
877 }
878 grpc_error* error = GRPC_ERROR_NONE;
879 for (int i = 0; (drain || i < handle_count) &&
880 pollable_obj->event_cursor != pollable_obj->event_count;
881 i++) {
882 int n = pollable_obj->event_cursor++;
883 struct epoll_event* ev = &pollable_obj->events[n];
884 void* data_ptr = ev->data.ptr;
885 if (1 & (intptr_t)data_ptr) {
886 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
887 gpr_log(GPR_INFO, "PS:%p got pollset_wakeup %p", pollset, data_ptr);
888 }
889 append_error(&error,
890 grpc_wakeup_fd_consume_wakeup(
891 (grpc_wakeup_fd*)((~static_cast<intptr_t>(1)) &
892 (intptr_t)data_ptr)),
893 err_desc);
894 } else {
895 grpc_fd* fd =
896 reinterpret_cast<grpc_fd*>(reinterpret_cast<intptr_t>(data_ptr) & ~2);
897 bool track_err = reinterpret_cast<intptr_t>(data_ptr) & 2;
898 bool cancel = (ev->events & EPOLLHUP) != 0;
899 bool error = (ev->events & EPOLLERR) != 0;
900 bool read_ev = (ev->events & (EPOLLIN | EPOLLPRI)) != 0;
901 bool write_ev = (ev->events & EPOLLOUT) != 0;
902 bool err_fallback = error && !track_err;
903
904 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
905 gpr_log(GPR_INFO,
906 "PS:%p got fd %p: cancel=%d read=%d "
907 "write=%d",
908 pollset, fd, cancel, read_ev, write_ev);
909 }
910 if (error && !err_fallback) {
911 fd_has_errors(fd);
912 }
913 if (read_ev || cancel || err_fallback) {
914 fd_become_readable(fd);
915 }
916 if (write_ev || cancel || err_fallback) {
917 fd_become_writable(fd);
918 }
919 }
920 }
921
922 return error;
923 }
924
925 /* pollset_shutdown is guaranteed to be called before pollset_destroy. */
926 static void pollset_destroy(grpc_pollset* pollset) {
927 POLLABLE_UNREF(pollset->active_pollable, "pollset");
928 pollset->active_pollable = nullptr;
929 gpr_mu_destroy(&pollset->mu);
930 }
931
932 static grpc_error* pollable_epoll(pollable* p, grpc_millis deadline) {
933 GPR_TIMER_SCOPE("pollable_epoll", 0);
934 int timeout = poll_deadline_to_millis_timeout(deadline);
935
936 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
937 char* desc = pollable_desc(p);
938 gpr_log(GPR_INFO, "POLLABLE:%p[%s] poll for %dms", p, desc, timeout);
939 gpr_free(desc);
940 }
941
942 if (timeout != 0) {
943 GRPC_SCHEDULING_START_BLOCKING_REGION;
944 }
945 int r;
946 do {
947 GRPC_STATS_INC_SYSCALL_POLL();
948 r = epoll_wait(p->epfd, p->events, MAX_EPOLL_EVENTS, timeout);
949 } while (r < 0 && errno == EINTR);
950 if (timeout != 0) {
951 GRPC_SCHEDULING_END_BLOCKING_REGION;
952 }
953
954 if (r < 0) return GRPC_OS_ERROR(errno, "epoll_wait");
955
956 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
957 gpr_log(GPR_INFO, "POLLABLE:%p got %d events", p, r);
958 }
959
960 p->event_cursor = 0;
961 p->event_count = r;
962
963 return GRPC_ERROR_NONE;
964 }
965
966 /* Return true if first in list */
967 static bool worker_insert(grpc_pollset_worker** root_worker,
968 grpc_pollset_worker* worker, pwlinks link) {
969 if (*root_worker == nullptr) {
970 *root_worker = worker;
971 worker->links[link].next = worker->links[link].prev = worker;
972 return true;
973 } else {
974 worker->links[link].next = *root_worker;
975 worker->links[link].prev = worker->links[link].next->links[link].prev;
976 worker->links[link].next->links[link].prev = worker;
977 worker->links[link].prev->links[link].next = worker;
978 return false;
979 }
980 }
981
982 /* returns the new root IFF the root changed */
983 typedef enum { WRR_NEW_ROOT, WRR_EMPTIED, WRR_REMOVED } worker_remove_result;
984
985 static worker_remove_result worker_remove(grpc_pollset_worker** root_worker,
986 grpc_pollset_worker* worker,
987 pwlinks link) {
988 if (worker == *root_worker) {
989 if (worker == worker->links[link].next) {
990 *root_worker = nullptr;
991 return WRR_EMPTIED;
992 } else {
993 *root_worker = worker->links[link].next;
994 worker->links[link].prev->links[link].next = worker->links[link].next;
995 worker->links[link].next->links[link].prev = worker->links[link].prev;
996 return WRR_NEW_ROOT;
997 }
998 } else {
999 worker->links[link].prev->links[link].next = worker->links[link].next;
1000 worker->links[link].next->links[link].prev = worker->links[link].prev;
1001 return WRR_REMOVED;
1002 }
1003 }
1004
1005 /* Return true if this thread should poll */
1006 static bool begin_worker(grpc_pollset* pollset, grpc_pollset_worker* worker,
1007 grpc_pollset_worker** worker_hdl,
1008 grpc_millis deadline) {
1009 GPR_TIMER_SCOPE("begin_worker", 0);
1010 bool do_poll =
1011 (pollset->shutdown_closure == nullptr && !pollset->already_shutdown);
1012 gpr_atm_no_barrier_fetch_add(&pollset->worker_count, 1);
1013 if (worker_hdl != nullptr) *worker_hdl = worker;
1014 worker->initialized_cv = false;
1015 worker->kicked = false;
1016 worker->pollset = pollset;
1017 worker->pollable_obj =
1018 POLLABLE_REF(pollset->active_pollable, "pollset_worker");
1019 worker_insert(&pollset->root_worker, worker, PWLINK_POLLSET);
1020 gpr_mu_lock(&worker->pollable_obj->mu);
1021 if (!worker_insert(&worker->pollable_obj->root_worker, worker,
1022 PWLINK_POLLABLE)) {
1023 worker->initialized_cv = true;
1024 gpr_cv_init(&worker->cv);
1025 gpr_mu_unlock(&pollset->mu);
1026 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace) &&
1027 worker->pollable_obj->root_worker != worker) {
1028 gpr_log(GPR_INFO, "PS:%p wait %p w=%p for %dms", pollset,
1029 worker->pollable_obj, worker,
1030 poll_deadline_to_millis_timeout(deadline));
1031 }
1032 while (do_poll && worker->pollable_obj->root_worker != worker) {
1033 if (gpr_cv_wait(&worker->cv, &worker->pollable_obj->mu,
1034 grpc_millis_to_timespec(deadline, GPR_CLOCK_REALTIME))) {
1035 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1036 gpr_log(GPR_INFO, "PS:%p timeout_wait %p w=%p", pollset,
1037 worker->pollable_obj, worker);
1038 }
1039 do_poll = false;
1040 } else if (worker->kicked) {
1041 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1042 gpr_log(GPR_INFO, "PS:%p wakeup %p w=%p", pollset,
1043 worker->pollable_obj, worker);
1044 }
1045 do_poll = false;
1046 } else if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace) &&
1047 worker->pollable_obj->root_worker != worker) {
1048 gpr_log(GPR_INFO, "PS:%p spurious_wakeup %p w=%p", pollset,
1049 worker->pollable_obj, worker);
1050 }
1051 }
1052 grpc_core::ExecCtx::Get()->InvalidateNow();
1053 } else {
1054 gpr_mu_unlock(&pollset->mu);
1055 }
1056 gpr_mu_unlock(&worker->pollable_obj->mu);
1057
1058 return do_poll;
1059 }
1060
1061 static void end_worker(grpc_pollset* pollset, grpc_pollset_worker* worker,
1062 grpc_pollset_worker** /*worker_hdl*/) {
1063 GPR_TIMER_SCOPE("end_worker", 0);
1064 gpr_mu_lock(&pollset->mu);
1065 gpr_mu_lock(&worker->pollable_obj->mu);
1066 switch (worker_remove(&worker->pollable_obj->root_worker, worker,
1067 PWLINK_POLLABLE)) {
1068 case WRR_NEW_ROOT: {
1069 // wakeup new poller
1070 grpc_pollset_worker* new_root = worker->pollable_obj->root_worker;
1071 GPR_ASSERT(new_root->initialized_cv);
1072 gpr_cv_signal(&new_root->cv);
1073 break;
1074 }
1075 case WRR_EMPTIED:
1076 if (pollset->active_pollable != worker->pollable_obj) {
1077 // pollable no longer being polled: flush events
1078 pollable_process_events(pollset, worker->pollable_obj, true);
1079 }
1080 break;
1081 case WRR_REMOVED:
1082 break;
1083 }
1084 gpr_mu_unlock(&worker->pollable_obj->mu);
1085 POLLABLE_UNREF(worker->pollable_obj, "pollset_worker");
1086 if (worker_remove(&pollset->root_worker, worker, PWLINK_POLLSET) ==
1087 WRR_EMPTIED) {
1088 pollset_maybe_finish_shutdown(pollset);
1089 }
1090 if (worker->initialized_cv) {
1091 gpr_cv_destroy(&worker->cv);
1092 }
1093 gpr_atm_no_barrier_fetch_add(&pollset->worker_count, -1);
1094 }
1095
1096 #ifndef NDEBUG
1097 static long sys_gettid(void) { return syscall(__NR_gettid); }
1098 #endif
1099
1100 /* pollset->mu lock must be held by the caller before calling this.
1101 The function pollset_work() may temporarily release the lock (pollset->po.mu)
1102 during the course of its execution but it will always re-acquire the lock and
1103 ensure that it is held by the time the function returns */
1104 static grpc_error* pollset_work(grpc_pollset* pollset,
1105 grpc_pollset_worker** worker_hdl,
1106 grpc_millis deadline) {
1107 GPR_TIMER_SCOPE("pollset_work", 0);
1108 #ifdef GRPC_EPOLLEX_CREATE_WORKERS_ON_HEAP
1109 grpc_pollset_worker* worker =
1110 (grpc_pollset_worker*)gpr_malloc(sizeof(*worker));
1111 #define WORKER_PTR (worker)
1112 #else
1113 grpc_pollset_worker worker;
1114 #define WORKER_PTR (&worker)
1115 #endif
1116 #ifndef NDEBUG
1117 WORKER_PTR->originator = sys_gettid();
1118 #endif
1119 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1120 gpr_log(GPR_INFO,
1121 "PS:%p work hdl=%p worker=%p now=%" PRId64 " deadline=%" PRId64
1122 " kwp=%d pollable=%p",
1123 pollset, worker_hdl, WORKER_PTR, grpc_core::ExecCtx::Get()->Now(),
1124 deadline, pollset->kicked_without_poller, pollset->active_pollable);
1125 }
1126 static const char* err_desc = "pollset_work";
1127 grpc_error* error = GRPC_ERROR_NONE;
1128 if (pollset->kicked_without_poller) {
1129 pollset->kicked_without_poller = false;
1130 } else {
1131 if (begin_worker(pollset, WORKER_PTR, worker_hdl, deadline)) {
1132 gpr_tls_set(&g_current_thread_pollset, (intptr_t)pollset);
1133 gpr_tls_set(&g_current_thread_worker, (intptr_t)WORKER_PTR);
1134 if (WORKER_PTR->pollable_obj->event_cursor ==
1135 WORKER_PTR->pollable_obj->event_count) {
1136 append_error(&error, pollable_epoll(WORKER_PTR->pollable_obj, deadline),
1137 err_desc);
1138 }
1139 append_error(
1140 &error,
1141 pollable_process_events(pollset, WORKER_PTR->pollable_obj, false),
1142 err_desc);
1143 grpc_core::ExecCtx::Get()->Flush();
1144 gpr_tls_set(&g_current_thread_pollset, 0);
1145 gpr_tls_set(&g_current_thread_worker, 0);
1146 }
1147 end_worker(pollset, WORKER_PTR, worker_hdl);
1148 }
1149 #ifdef GRPC_EPOLLEX_CREATE_WORKERS_ON_HEAP
1150 gpr_free(worker);
1151 #endif
1152 #undef WORKER_PTR
1153 return error;
1154 }
1155
1156 static grpc_error* pollset_transition_pollable_from_empty_to_fd_locked(
1157 grpc_pollset* pollset, grpc_fd* fd) {
1158 static const char* err_desc = "pollset_transition_pollable_from_empty_to_fd";
1159 grpc_error* error = GRPC_ERROR_NONE;
1160 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1161 gpr_log(GPR_INFO,
1162 "PS:%p add fd %p (%d); transition pollable from empty to fd",
1163 pollset, fd, fd->fd);
1164 }
1165 append_error(&error, pollset_kick_all(pollset), err_desc);
1166 POLLABLE_UNREF(pollset->active_pollable, "pollset");
1167 append_error(&error, get_fd_pollable(fd, &pollset->active_pollable),
1168 err_desc);
1169 return error;
1170 }
1171
1172 static grpc_error* pollset_transition_pollable_from_fd_to_multi_locked(
1173 grpc_pollset* pollset, grpc_fd* and_add_fd) {
1174 static const char* err_desc = "pollset_transition_pollable_from_fd_to_multi";
1175 grpc_error* error = GRPC_ERROR_NONE;
1176 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1177 gpr_log(
1178 GPR_INFO,
1179 "PS:%p add fd %p (%d); transition pollable from fd %p to multipoller",
1180 pollset, and_add_fd, and_add_fd ? and_add_fd->fd : -1,
1181 pollset->active_pollable->owner_fd);
1182 }
1183 append_error(&error, pollset_kick_all(pollset), err_desc);
1184 grpc_fd* initial_fd = pollset->active_pollable->owner_fd;
1185 POLLABLE_UNREF(pollset->active_pollable, "pollset");
1186 pollset->active_pollable = nullptr;
1187 if (append_error(&error, pollable_create(PO_MULTI, &pollset->active_pollable),
1188 err_desc)) {
1189 append_error(&error, pollable_add_fd(pollset->active_pollable, initial_fd),
1190 err_desc);
1191 if (and_add_fd != nullptr) {
1192 append_error(&error,
1193 pollable_add_fd(pollset->active_pollable, and_add_fd),
1194 err_desc);
1195 }
1196 }
1197 return error;
1198 }
1199
1200 /* expects pollsets locked, flag whether fd is locked or not */
1201 static grpc_error* pollset_add_fd_locked(grpc_pollset* pollset, grpc_fd* fd) {
1202 grpc_error* error = GRPC_ERROR_NONE;
1203 pollable* po_at_start =
1204 POLLABLE_REF(pollset->active_pollable, "pollset_add_fd");
1205 switch (pollset->active_pollable->type) {
1206 case PO_EMPTY:
1207 /* empty pollable --> single fd pollable */
1208 error = pollset_transition_pollable_from_empty_to_fd_locked(pollset, fd);
1209 break;
1210 case PO_FD:
1211 gpr_mu_lock(&po_at_start->owner_orphan_mu);
1212 if (po_at_start->owner_orphaned) {
1213 error =
1214 pollset_transition_pollable_from_empty_to_fd_locked(pollset, fd);
1215 } else {
1216 /* fd --> multipoller */
1217 error =
1218 pollset_transition_pollable_from_fd_to_multi_locked(pollset, fd);
1219 }
1220 gpr_mu_unlock(&po_at_start->owner_orphan_mu);
1221 break;
1222 case PO_MULTI:
1223 error = pollable_add_fd(pollset->active_pollable, fd);
1224 break;
1225 }
1226 if (error != GRPC_ERROR_NONE) {
1227 POLLABLE_UNREF(pollset->active_pollable, "pollset");
1228 pollset->active_pollable = po_at_start;
1229 } else {
1230 gpr_atm_rel_store(&pollset->active_pollable_type,
1231 pollset->active_pollable->type);
1232 POLLABLE_UNREF(po_at_start, "pollset_add_fd");
1233 }
1234 return error;
1235 }
1236
1237 static grpc_error* pollset_as_multipollable_locked(grpc_pollset* pollset,
1238 pollable** pollable_obj) {
1239 grpc_error* error = GRPC_ERROR_NONE;
1240 pollable* po_at_start =
1241 POLLABLE_REF(pollset->active_pollable, "pollset_as_multipollable");
1242 switch (pollset->active_pollable->type) {
1243 case PO_EMPTY:
1244 POLLABLE_UNREF(pollset->active_pollable, "pollset");
1245 error = pollable_create(PO_MULTI, &pollset->active_pollable);
1246 /* Any workers currently polling on this pollset must now be woked up so
1247 * that they can pick up the new active_pollable */
1248 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1249 gpr_log(GPR_INFO,
1250 "PS:%p active pollable transition from empty to multi",
1251 pollset);
1252 }
1253 static const char* err_desc =
1254 "pollset_as_multipollable_locked: empty -> multi";
1255 append_error(&error, pollset_kick_all(pollset), err_desc);
1256 break;
1257 case PO_FD:
1258 gpr_mu_lock(&po_at_start->owner_orphan_mu);
1259 if (po_at_start->owner_orphaned) {
1260 // Unlock before Unref'ing the pollable
1261 gpr_mu_unlock(&po_at_start->owner_orphan_mu);
1262 POLLABLE_UNREF(pollset->active_pollable, "pollset");
1263 error = pollable_create(PO_MULTI, &pollset->active_pollable);
1264 } else {
1265 error = pollset_transition_pollable_from_fd_to_multi_locked(pollset,
1266 nullptr);
1267 gpr_mu_unlock(&po_at_start->owner_orphan_mu);
1268 }
1269 break;
1270 case PO_MULTI:
1271 break;
1272 }
1273 if (error != GRPC_ERROR_NONE) {
1274 POLLABLE_UNREF(pollset->active_pollable, "pollset");
1275 pollset->active_pollable = po_at_start;
1276 *pollable_obj = nullptr;
1277 } else {
1278 gpr_atm_rel_store(&pollset->active_pollable_type,
1279 pollset->active_pollable->type);
1280 *pollable_obj = POLLABLE_REF(pollset->active_pollable, "pollset_set");
1281 POLLABLE_UNREF(po_at_start, "pollset_as_multipollable");
1282 }
1283 return error;
1284 }
1285
1286 static void pollset_add_fd(grpc_pollset* pollset, grpc_fd* fd) {
1287 GPR_TIMER_SCOPE("pollset_add_fd", 0);
1288
1289 // We never transition from PO_MULTI to other modes (i.e., PO_FD or PO_EMPTY)
1290 // and, thus, it is safe to simply store and check whether the FD has already
1291 // been added to the active pollable previously.
1292 if (gpr_atm_acq_load(&pollset->active_pollable_type) == PO_MULTI &&
1293 fd_has_pollset(fd, pollset)) {
1294 return;
1295 }
1296
1297 grpc_core::MutexLock lock(&pollset->mu);
1298 grpc_error* error = pollset_add_fd_locked(pollset, fd);
1299
1300 // If we are in PO_MULTI mode, we should update the pollsets of the FD.
1301 if (gpr_atm_no_barrier_load(&pollset->active_pollable_type) == PO_MULTI) {
1302 fd_add_pollset(fd, pollset);
1303 }
1304
1305 GRPC_LOG_IF_ERROR("pollset_add_fd", error);
1306 }
1307
1308 /*******************************************************************************
1309 * Pollset-set Definitions
1310 */
1311
1312 static grpc_pollset_set* pss_lock_adam(grpc_pollset_set* pss) {
1313 gpr_mu_lock(&pss->mu);
1314 while (pss->parent != nullptr) {
1315 gpr_mu_unlock(&pss->mu);
1316 pss = pss->parent;
1317 gpr_mu_lock(&pss->mu);
1318 }
1319 return pss;
1320 }
1321
1322 static grpc_pollset_set* pollset_set_create(void) {
1323 grpc_pollset_set* pss =
1324 static_cast<grpc_pollset_set*>(gpr_zalloc(sizeof(*pss)));
1325 gpr_mu_init(&pss->mu);
1326 new (&pss->refs) grpc_core::RefCount();
1327 return pss;
1328 }
1329
1330 static void pollset_set_unref(grpc_pollset_set* pss) {
1331 if (pss == nullptr) return;
1332 if (GPR_LIKELY(!pss->refs.Unref())) return;
1333 pollset_set_unref(pss->parent);
1334 gpr_mu_destroy(&pss->mu);
1335 for (size_t i = 0; i < pss->pollset_count; i++) {
1336 gpr_mu_lock(&pss->pollsets[i]->mu);
1337 if (0 == --pss->pollsets[i]->containing_pollset_set_count) {
1338 pollset_maybe_finish_shutdown(pss->pollsets[i]);
1339 }
1340 gpr_mu_unlock(&pss->pollsets[i]->mu);
1341 }
1342 for (size_t i = 0; i < pss->fd_count; i++) {
1343 UNREF_BY(pss->fds[i], 2, "pollset_set");
1344 }
1345 gpr_free(pss->pollsets);
1346 gpr_free(pss->fds);
1347 gpr_free(pss);
1348 }
1349
1350 static void pollset_set_add_fd(grpc_pollset_set* pss, grpc_fd* fd) {
1351 GPR_TIMER_SCOPE("pollset_set_add_fd", 0);
1352 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1353 gpr_log(GPR_INFO, "PSS:%p: add fd %p (%d)", pss, fd, fd->fd);
1354 }
1355 grpc_error* error = GRPC_ERROR_NONE;
1356 static const char* err_desc = "pollset_set_add_fd";
1357 pss = pss_lock_adam(pss);
1358 for (size_t i = 0; i < pss->pollset_count; i++) {
1359 append_error(&error, pollable_add_fd(pss->pollsets[i]->active_pollable, fd),
1360 err_desc);
1361 }
1362 if (pss->fd_count == pss->fd_capacity) {
1363 pss->fd_capacity = GPR_MAX(pss->fd_capacity * 2, 8);
1364 pss->fds = static_cast<grpc_fd**>(
1365 gpr_realloc(pss->fds, pss->fd_capacity * sizeof(*pss->fds)));
1366 }
1367 REF_BY(fd, 2, "pollset_set");
1368 pss->fds[pss->fd_count++] = fd;
1369 gpr_mu_unlock(&pss->mu);
1370
1371 GRPC_LOG_IF_ERROR(err_desc, error);
1372 }
1373
1374 static void pollset_set_del_fd(grpc_pollset_set* pss, grpc_fd* fd) {
1375 GPR_TIMER_SCOPE("pollset_set_del_fd", 0);
1376 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1377 gpr_log(GPR_INFO, "PSS:%p: del fd %p", pss, fd);
1378 }
1379 pss = pss_lock_adam(pss);
1380 size_t i;
1381 for (i = 0; i < pss->fd_count; i++) {
1382 if (pss->fds[i] == fd) {
1383 UNREF_BY(fd, 2, "pollset_set");
1384 break;
1385 }
1386 }
1387 GPR_ASSERT(i != pss->fd_count);
1388 for (; i < pss->fd_count - 1; i++) {
1389 pss->fds[i] = pss->fds[i + 1];
1390 }
1391 pss->fd_count--;
1392 gpr_mu_unlock(&pss->mu);
1393 }
1394
1395 static void pollset_set_del_pollset(grpc_pollset_set* pss, grpc_pollset* ps) {
1396 GPR_TIMER_SCOPE("pollset_set_del_pollset", 0);
1397 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1398 gpr_log(GPR_INFO, "PSS:%p: del pollset %p", pss, ps);
1399 }
1400 pss = pss_lock_adam(pss);
1401 size_t i;
1402 for (i = 0; i < pss->pollset_count; i++) {
1403 if (pss->pollsets[i] == ps) {
1404 break;
1405 }
1406 }
1407 GPR_ASSERT(i != pss->pollset_count);
1408 for (; i < pss->pollset_count - 1; i++) {
1409 pss->pollsets[i] = pss->pollsets[i + 1];
1410 }
1411 pss->pollset_count--;
1412 gpr_mu_unlock(&pss->mu);
1413 gpr_mu_lock(&ps->mu);
1414 if (0 == --ps->containing_pollset_set_count) {
1415 pollset_maybe_finish_shutdown(ps);
1416 }
1417 gpr_mu_unlock(&ps->mu);
1418 }
1419
1420 // add all fds to pollables, and output a new array of unorphaned out_fds
1421 // assumes pollsets are multipollable
1422 static grpc_error* add_fds_to_pollsets(grpc_fd** fds, size_t fd_count,
1423 grpc_pollset** pollsets,
1424 size_t pollset_count,
1425 const char* err_desc, grpc_fd** out_fds,
1426 size_t* out_fd_count) {
1427 GPR_TIMER_SCOPE("add_fds_to_pollsets", 0);
1428 grpc_error* error = GRPC_ERROR_NONE;
1429 for (size_t i = 0; i < fd_count; i++) {
1430 gpr_mu_lock(&fds[i]->orphan_mu);
1431 if ((gpr_atm_no_barrier_load(&fds[i]->refst) & 1) == 0) {
1432 gpr_mu_unlock(&fds[i]->orphan_mu);
1433 UNREF_BY(fds[i], 2, "pollset_set");
1434 } else {
1435 for (size_t j = 0; j < pollset_count; j++) {
1436 append_error(&error,
1437 pollable_add_fd(pollsets[j]->active_pollable, fds[i]),
1438 err_desc);
1439 }
1440 gpr_mu_unlock(&fds[i]->orphan_mu);
1441 out_fds[(*out_fd_count)++] = fds[i];
1442 }
1443 }
1444 return error;
1445 }
1446
1447 static void pollset_set_add_pollset(grpc_pollset_set* pss, grpc_pollset* ps) {
1448 GPR_TIMER_SCOPE("pollset_set_add_pollset", 0);
1449 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1450 gpr_log(GPR_INFO, "PSS:%p: add pollset %p", pss, ps);
1451 }
1452 grpc_error* error = GRPC_ERROR_NONE;
1453 static const char* err_desc = "pollset_set_add_pollset";
1454 pollable* pollable_obj = nullptr;
1455 gpr_mu_lock(&ps->mu);
1456 if (!GRPC_LOG_IF_ERROR(err_desc,
1457 pollset_as_multipollable_locked(ps, &pollable_obj))) {
1458 GPR_ASSERT(pollable_obj == nullptr);
1459 gpr_mu_unlock(&ps->mu);
1460 return;
1461 }
1462 ps->containing_pollset_set_count++;
1463 gpr_mu_unlock(&ps->mu);
1464 pss = pss_lock_adam(pss);
1465 size_t initial_fd_count = pss->fd_count;
1466 pss->fd_count = 0;
1467 append_error(&error,
1468 add_fds_to_pollsets(pss->fds, initial_fd_count, &ps, 1, err_desc,
1469 pss->fds, &pss->fd_count),
1470 err_desc);
1471 if (pss->pollset_count == pss->pollset_capacity) {
1472 pss->pollset_capacity = GPR_MAX(pss->pollset_capacity * 2, 8);
1473 pss->pollsets = static_cast<grpc_pollset**>(gpr_realloc(
1474 pss->pollsets, pss->pollset_capacity * sizeof(*pss->pollsets)));
1475 }
1476 pss->pollsets[pss->pollset_count++] = ps;
1477 gpr_mu_unlock(&pss->mu);
1478 POLLABLE_UNREF(pollable_obj, "pollset_set");
1479
1480 GRPC_LOG_IF_ERROR(err_desc, error);
1481 }
1482
1483 static void pollset_set_add_pollset_set(grpc_pollset_set* a,
1484 grpc_pollset_set* b) {
1485 GPR_TIMER_SCOPE("pollset_set_add_pollset_set", 0);
1486 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1487 gpr_log(GPR_INFO, "PSS: merge (%p, %p)", a, b);
1488 }
1489 grpc_error* error = GRPC_ERROR_NONE;
1490 static const char* err_desc = "pollset_set_add_fd";
1491 for (;;) {
1492 if (a == b) {
1493 // pollset ancestors are the same: nothing to do
1494 return;
1495 }
1496 if (a > b) {
1497 GPR_SWAP(grpc_pollset_set*, a, b);
1498 }
1499 gpr_mu* a_mu = &a->mu;
1500 gpr_mu* b_mu = &b->mu;
1501 gpr_mu_lock(a_mu);
1502 gpr_mu_lock(b_mu);
1503 if (a->parent != nullptr) {
1504 a = a->parent;
1505 } else if (b->parent != nullptr) {
1506 b = b->parent;
1507 } else {
1508 break; // exit loop, both pollsets locked
1509 }
1510 gpr_mu_unlock(a_mu);
1511 gpr_mu_unlock(b_mu);
1512 }
1513 // try to do the least copying possible
1514 // TODO(sreek): there's probably a better heuristic here
1515 const size_t a_size = a->fd_count + a->pollset_count;
1516 const size_t b_size = b->fd_count + b->pollset_count;
1517 if (b_size > a_size) {
1518 GPR_SWAP(grpc_pollset_set*, a, b);
1519 }
1520 if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
1521 gpr_log(GPR_INFO, "PSS: parent %p to %p", b, a);
1522 }
1523 a->refs.Ref();
1524 b->parent = a;
1525 if (a->fd_capacity < a->fd_count + b->fd_count) {
1526 a->fd_capacity = GPR_MAX(2 * a->fd_capacity, a->fd_count + b->fd_count);
1527 a->fds = static_cast<grpc_fd**>(
1528 gpr_realloc(a->fds, a->fd_capacity * sizeof(*a->fds)));
1529 }
1530 size_t initial_a_fd_count = a->fd_count;
1531 a->fd_count = 0;
1532 append_error(
1533 &error,
1534 add_fds_to_pollsets(a->fds, initial_a_fd_count, b->pollsets,
1535 b->pollset_count, "merge_a2b", a->fds, &a->fd_count),
1536 err_desc);
1537 append_error(
1538 &error,
1539 add_fds_to_pollsets(b->fds, b->fd_count, a->pollsets, a->pollset_count,
1540 "merge_b2a", a->fds, &a->fd_count),
1541 err_desc);
1542 if (a->pollset_capacity < a->pollset_count + b->pollset_count) {
1543 a->pollset_capacity =
1544 GPR_MAX(2 * a->pollset_capacity, a->pollset_count + b->pollset_count);
1545 a->pollsets = static_cast<grpc_pollset**>(
1546 gpr_realloc(a->pollsets, a->pollset_capacity * sizeof(*a->pollsets)));
1547 }
1548 if (b->pollset_count > 0) {
1549 memcpy(a->pollsets + a->pollset_count, b->pollsets,
1550 b->pollset_count * sizeof(*b->pollsets));
1551 }
1552 a->pollset_count += b->pollset_count;
1553 gpr_free(b->fds);
1554 gpr_free(b->pollsets);
1555 b->fds = nullptr;
1556 b->pollsets = nullptr;
1557 b->fd_count = b->fd_capacity = b->pollset_count = b->pollset_capacity = 0;
1558 gpr_mu_unlock(&a->mu);
1559 gpr_mu_unlock(&b->mu);
1560 }
1561
1562 static void pollset_set_del_pollset_set(grpc_pollset_set* /*bag*/,
1563 grpc_pollset_set* /*item*/) {}
1564
1565 /*******************************************************************************
1566 * Event engine binding
1567 */
1568
1569 static bool is_any_background_poller_thread(void) { return false; }
1570
1571 static void shutdown_background_closure(void) {}
1572
1573 static bool add_closure_to_background_poller(grpc_closure* /*closure*/,
1574 grpc_error* /*error*/) {
1575 return false;
1576 }
1577
1578 static void shutdown_engine(void) {
1579 fd_global_shutdown();
1580 pollset_global_shutdown();
1581 }
1582
1583 static const grpc_event_engine_vtable vtable = {
1584 sizeof(grpc_pollset),
1585 true,
1586 false,
1587
1588 fd_create,
1589 fd_wrapped_fd,
1590 fd_orphan,
1591 fd_shutdown,
1592 fd_notify_on_read,
1593 fd_notify_on_write,
1594 fd_notify_on_error,
1595 fd_become_readable,
1596 fd_become_writable,
1597 fd_has_errors,
1598 fd_is_shutdown,
1599
1600 pollset_init,
1601 pollset_shutdown,
1602 pollset_destroy,
1603 pollset_work,
1604 pollset_kick,
1605 pollset_add_fd,
1606
1607 pollset_set_create,
1608 pollset_set_unref, // destroy ==> unref 1 public ref
1609 pollset_set_add_pollset,
1610 pollset_set_del_pollset,
1611 pollset_set_add_pollset_set,
1612 pollset_set_del_pollset_set,
1613 pollset_set_add_fd,
1614 pollset_set_del_fd,
1615
1616 is_any_background_poller_thread,
1617 shutdown_background_closure,
1618 shutdown_engine,
1619 add_closure_to_background_poller,
1620 };
1621
1622 const grpc_event_engine_vtable* grpc_init_epollex_linux(
1623 bool /*explicitly_requested*/) {
1624 if (!grpc_has_wakeup_fd()) {
1625 gpr_log(GPR_ERROR, "Skipping epollex because of no wakeup fd.");
1626 return nullptr;
1627 }
1628
1629 if (!grpc_is_epollexclusive_available()) {
1630 gpr_log(GPR_INFO, "Skipping epollex because it is not supported.");
1631 return nullptr;
1632 }
1633
1634 fd_global_init();
1635
1636 if (!GRPC_LOG_IF_ERROR("pollset_global_init", pollset_global_init())) {
1637 pollset_global_shutdown();
1638 fd_global_shutdown();
1639 return nullptr;
1640 }
1641
1642 return &vtable;
1643 }
1644
1645 #else /* defined(GRPC_LINUX_EPOLL_CREATE1) */
1646 #if defined(GRPC_POSIX_SOCKET_EV_EPOLLEX)
1647 #include "src/core/lib/iomgr/ev_epollex_linux.h"
1648 /* If GRPC_LINUX_EPOLL_CREATE1 is not defined, it means
1649 epoll_create1 is not available. Return NULL */
1650 const grpc_event_engine_vtable* grpc_init_epollex_linux(
1651 bool /*explicitly_requested*/) {
1652 return nullptr;
1653 }
1654 #endif /* defined(GRPC_POSIX_SOCKET_EV_EPOLLEX) */
1655
1656 #endif /* !defined(GRPC_LINUX_EPOLL_CREATE1) */
1657