Revision tags: v6.2.1, v6.2.0, v6.3.0, v6.0.1, v6.0.0, v6.0.0rc1, v6.1.0, v5.8.3, v5.8.2, v5.8.1, v5.8.0, v5.9.0, v5.8.0rc1, v5.6.3 |
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721505de |
| 12-Nov-2019 |
Matthew Dillon <dillon@apollo.backplane.com> |
libc - Implement sigblockall() and sigunblockall()
* Signal safety is becoming a defacto requirement for most of libc and pthreads. In particular, the memory allocator. Given the chances of te
libc - Implement sigblockall() and sigunblockall()
* Signal safety is becoming a defacto requirement for most of libc and pthreads. In particular, the memory allocator. Given the chances of teaching tens of thousands of programmers about signal safety, and just making it work in libc and pthreads, only one of these two possibilities is actually realizable.
In particular, high-level languages have become so complex, and some applications (chrome, firefox, etc) have become so complex, that the code is regularly tripping over signal safety issues.
However, implementing signal safety with current mechanisms is extremely expensive due to the need for multiple system calls. To whit, DragonFlyBSD now has a mechanism that does not require system calls in the critical path.
* Implement sigblockall() and sigunblockall(). These functions leverage the new /dev/lpmap per-thread shared page mechanism to provide a way to temporary block the dispatch of all maskable signals without having to make any system calls.
These are extremely fast routines.
- Reentrant / Recursable
- Temporarily blocks any dispatch of a maskable asynchronous signal to the calling thread. Other threads are not affected... this is a per-thread mechanism.
- The last sigunblockall() will immediately dispatch any blocked signals.
- The normal signal mask is not affected by these routines.
- Does not block signals caused by synchronous traps.
- The current recursion count is retained on [v]fork() to ease coding and to also allow signals to be temporarily blocked across a fork until the child process is ready to deal with them, if desired.
* Implement signal safety for most of pthreads. All temporary internal mutexes are now wrapped with sigblockall() and sigunblockall().
* Implement signal safety for the malloc subsystem. All functions are wrawpped with sigblockall() and sigunblockall().
These implementations make lang/mono and lang/rust far more reliable than they were before. Where 9 out of 10 builds used to fail, now they succeed.
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Revision tags: v5.6.2, v5.6.1, v5.6.0, v5.6.0rc1, v5.7.0, v5.4.3, v5.4.2, v5.4.1, v5.4.0, v5.5.0, v5.4.0rc1, v5.2.2, v5.2.1, v5.2.0, v5.3.0, v5.2.0rc, v5.0.2, v5.0.1, v5.0.0, v5.0.0rc2, v5.1.0, v5.0.0rc1, v4.8.1, v4.8.0, v4.6.2, v4.9.0, v4.8.0rc, v4.6.1, v4.6.0, v4.6.0rc2, v4.6.0rc, v4.7.0, v4.4.3, v4.4.2, v4.4.1, v4.4.0, v4.5.0, v4.4.0rc, v4.2.4, v4.3.1, v4.2.3, v4.2.1, v4.2.0, v4.0.6, v4.3.0, v4.2.0rc, v4.0.5, v4.0.4, v4.0.3, v4.0.2, v4.0.1, v4.0.0, v4.0.0rc3, v4.0.0rc2, v4.0.0rc, v4.1.0 |
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87116512 |
| 17-Oct-2014 |
Matthew Dillon <dillon@apollo.backplane.com> |
kernel - Add /dev/upmap and /dev/kpmap and sys/upmap.h (3)
* Add upmap->invfork. When a vforked child is trying to access the upmap prior to exec we must still access the parent's map and not the
kernel - Add /dev/upmap and /dev/kpmap and sys/upmap.h (3)
* Add upmap->invfork. When a vforked child is trying to access the upmap prior to exec we must still access the parent's map and not the child's, which means that the stored PID will be incorrect.
To fix this issue we add the invfork field which allows userland to determine whether this is a vforked child accessing the parent's map. If it is, getpid() will use the system call.
* Fix a bug where a vfork()d child creates p->p_upmap for itself but then maps it into the parent's address space as a side effect of a getpid() or other call. When this situation is detected, /dev/upmap will use the parent's p_upmap and not the child's, and also properly set the invfork flag.
* Implement system call overrides for getpid(), setproctitle(), and clock_gettime() (*_FAST and *_SECOND clock ids). When more than 10 calls are made to one of these functions the new libc upmap/kpmap support is activated. /dev/upmap and /dev/kpmap will be memory-mapped into the address space and further accesses will run through the maps instead of making system calls.
This will obviously reduce overhead for these calls by a very significant multiplier.
* NOTE! gettimeofday() is still a system call and will likely remain a system call in order to return a fine-grained time value. Third-party code that doesn't need a fine-grained time value must use clock_gettime() to obtain the new performance efficiencies.
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