1 /* 2 * QEMU coroutine implementation 3 * 4 * Copyright IBM, Corp. 2011 5 * 6 * Authors: 7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> 8 * Kevin Wolf <kwolf@redhat.com> 9 * 10 * This work is licensed under the terms of the GNU LGPL, version 2 or later. 11 * See the COPYING.LIB file in the top-level directory. 12 * 13 */ 14 15 #ifndef QEMU_COROUTINE_CORE_H 16 #define QEMU_COROUTINE_CORE_H 17 18 /** 19 * Coroutines are a mechanism for stack switching and can be used for 20 * cooperative userspace threading. These functions provide a simple but 21 * useful flavor of coroutines that is suitable for writing sequential code, 22 * rather than callbacks, for operations that need to give up control while 23 * waiting for events to complete. 24 * 25 * These functions are re-entrant and may be used outside the BQL. 26 * 27 * Functions that execute in coroutine context cannot be called 28 * directly from normal functions. Use @coroutine_fn to mark such 29 * functions. For example: 30 * 31 * static void coroutine_fn foo(void) { 32 * .... 33 * } 34 * 35 * In the future it would be nice to have the compiler or a static 36 * checker catch misuse of such functions. This annotation might make 37 * it possible and in the meantime it serves as documentation. 38 */ 39 40 /** 41 * Mark a function that executes in coroutine context 42 * 43 * 44 * Functions that execute in coroutine context cannot be called 45 * directly from normal functions. Use @coroutine_fn to mark such 46 * functions. For example: 47 * 48 * static void coroutine_fn foo(void) { 49 * .... 50 * } 51 * 52 * In the future it would be nice to have the compiler or a static 53 * checker catch misuse of such functions. This annotation might make 54 * it possible and in the meantime it serves as documentation. 55 */ 56 57 typedef struct Coroutine Coroutine; 58 typedef struct CoMutex CoMutex; 59 60 /** 61 * Coroutine entry point 62 * 63 * When the coroutine is entered for the first time, opaque is passed in as an 64 * argument. 65 * 66 * When this function returns, the coroutine is destroyed automatically and 67 * execution continues in the caller who last entered the coroutine. 68 */ 69 typedef void coroutine_fn CoroutineEntry(void *opaque); 70 71 /** 72 * Create a new coroutine 73 * 74 * Use qemu_coroutine_enter() to actually transfer control to the coroutine. 75 * The opaque argument is passed as the argument to the entry point. 76 */ 77 Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque); 78 79 /** 80 * Transfer control to a coroutine 81 */ 82 void qemu_coroutine_enter(Coroutine *coroutine); 83 84 /** 85 * Transfer control to a coroutine if it's not active (i.e. part of the call 86 * stack of the running coroutine). Otherwise, do nothing. 87 */ 88 void qemu_coroutine_enter_if_inactive(Coroutine *co); 89 90 /** 91 * Transfer control to a coroutine and associate it with ctx 92 */ 93 void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co); 94 95 /** 96 * Transfer control back to a coroutine's caller 97 * 98 * This function does not return until the coroutine is re-entered using 99 * qemu_coroutine_enter(). 100 */ 101 void coroutine_fn qemu_coroutine_yield(void); 102 103 /** 104 * Get the AioContext of the given coroutine 105 */ 106 AioContext *qemu_coroutine_get_aio_context(Coroutine *co); 107 108 /** 109 * Get the currently executing coroutine 110 */ 111 Coroutine *qemu_coroutine_self(void); 112 113 /** 114 * Return whether or not currently inside a coroutine 115 * 116 * This can be used to write functions that work both when in coroutine context 117 * and when not in coroutine context. Note that such functions cannot use the 118 * coroutine_fn annotation since they work outside coroutine context. 119 */ 120 bool qemu_in_coroutine(void); 121 122 /** 123 * Return true if the coroutine is currently entered 124 * 125 * A coroutine is "entered" if it has not yielded from the current 126 * qemu_coroutine_enter() call used to run it. This does not mean that the 127 * coroutine is currently executing code since it may have transferred control 128 * to another coroutine using qemu_coroutine_enter(). 129 * 130 * When several coroutines enter each other there may be no way to know which 131 * ones have already been entered. In such situations this function can be 132 * used to avoid recursively entering coroutines. 133 */ 134 bool qemu_coroutine_entered(Coroutine *co); 135 136 /** 137 * Initialises a CoMutex. This must be called before any other operation is used 138 * on the CoMutex. 139 */ 140 void qemu_co_mutex_init(CoMutex *mutex); 141 142 /** 143 * Locks the mutex. If the lock cannot be taken immediately, control is 144 * transferred to the caller of the current coroutine. 145 */ 146 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex); 147 148 /** 149 * Unlocks the mutex and schedules the next coroutine that was waiting for this 150 * lock to be run. 151 */ 152 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex); 153 154 #endif 155