1 /* 2 * QEMU coroutines 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 #include "qemu/osdep.h" 16 #include "trace.h" 17 #include "qemu-common.h" 18 #include "qemu/thread.h" 19 #include "qemu/atomic.h" 20 #include "qemu/coroutine.h" 21 #include "qemu/coroutine_int.h" 22 #include "block/aio.h" 23 24 enum { 25 POOL_BATCH_SIZE = 64, 26 }; 27 28 /** Free list to speed up creation */ 29 static QSLIST_HEAD(, Coroutine) release_pool = QSLIST_HEAD_INITIALIZER(pool); 30 static unsigned int release_pool_size; 31 static __thread QSLIST_HEAD(, Coroutine) alloc_pool = QSLIST_HEAD_INITIALIZER(pool); 32 static __thread unsigned int alloc_pool_size; 33 static __thread Notifier coroutine_pool_cleanup_notifier; 34 35 static void coroutine_pool_cleanup(Notifier *n, void *value) 36 { 37 Coroutine *co; 38 Coroutine *tmp; 39 40 QSLIST_FOREACH_SAFE(co, &alloc_pool, pool_next, tmp) { 41 QSLIST_REMOVE_HEAD(&alloc_pool, pool_next); 42 qemu_coroutine_delete(co); 43 } 44 } 45 46 Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque) 47 { 48 Coroutine *co = NULL; 49 50 if (CONFIG_COROUTINE_POOL) { 51 co = QSLIST_FIRST(&alloc_pool); 52 if (!co) { 53 if (release_pool_size > POOL_BATCH_SIZE) { 54 /* Slow path; a good place to register the destructor, too. */ 55 if (!coroutine_pool_cleanup_notifier.notify) { 56 coroutine_pool_cleanup_notifier.notify = coroutine_pool_cleanup; 57 qemu_thread_atexit_add(&coroutine_pool_cleanup_notifier); 58 } 59 60 /* This is not exact; there could be a little skew between 61 * release_pool_size and the actual size of release_pool. But 62 * it is just a heuristic, it does not need to be perfect. 63 */ 64 alloc_pool_size = atomic_xchg(&release_pool_size, 0); 65 QSLIST_MOVE_ATOMIC(&alloc_pool, &release_pool); 66 co = QSLIST_FIRST(&alloc_pool); 67 } 68 } 69 if (co) { 70 QSLIST_REMOVE_HEAD(&alloc_pool, pool_next); 71 alloc_pool_size--; 72 } 73 } 74 75 if (!co) { 76 co = qemu_coroutine_new(); 77 } 78 79 co->entry = entry; 80 co->entry_arg = opaque; 81 QSIMPLEQ_INIT(&co->co_queue_wakeup); 82 return co; 83 } 84 85 static void coroutine_delete(Coroutine *co) 86 { 87 co->caller = NULL; 88 89 if (CONFIG_COROUTINE_POOL) { 90 if (release_pool_size < POOL_BATCH_SIZE * 2) { 91 QSLIST_INSERT_HEAD_ATOMIC(&release_pool, co, pool_next); 92 atomic_inc(&release_pool_size); 93 return; 94 } 95 if (alloc_pool_size < POOL_BATCH_SIZE) { 96 QSLIST_INSERT_HEAD(&alloc_pool, co, pool_next); 97 alloc_pool_size++; 98 return; 99 } 100 } 101 102 qemu_coroutine_delete(co); 103 } 104 105 void qemu_coroutine_enter(Coroutine *co) 106 { 107 Coroutine *self = qemu_coroutine_self(); 108 CoroutineAction ret; 109 110 trace_qemu_coroutine_enter(self, co, co->entry_arg); 111 112 if (co->caller) { 113 fprintf(stderr, "Co-routine re-entered recursively\n"); 114 abort(); 115 } 116 117 co->caller = self; 118 co->ctx = qemu_get_current_aio_context(); 119 120 /* Store co->ctx before anything that stores co. Matches 121 * barrier in aio_co_wake and qemu_co_mutex_wake. 122 */ 123 smp_wmb(); 124 125 ret = qemu_coroutine_switch(self, co, COROUTINE_ENTER); 126 127 qemu_co_queue_run_restart(co); 128 129 switch (ret) { 130 case COROUTINE_YIELD: 131 return; 132 case COROUTINE_TERMINATE: 133 assert(!co->locks_held); 134 trace_qemu_coroutine_terminate(co); 135 coroutine_delete(co); 136 return; 137 default: 138 abort(); 139 } 140 } 141 142 void qemu_coroutine_enter_if_inactive(Coroutine *co) 143 { 144 if (!qemu_coroutine_entered(co)) { 145 qemu_coroutine_enter(co); 146 } 147 } 148 149 void coroutine_fn qemu_coroutine_yield(void) 150 { 151 Coroutine *self = qemu_coroutine_self(); 152 Coroutine *to = self->caller; 153 154 trace_qemu_coroutine_yield(self, to); 155 156 if (!to) { 157 fprintf(stderr, "Co-routine is yielding to no one\n"); 158 abort(); 159 } 160 161 self->caller = NULL; 162 qemu_coroutine_switch(self, to, COROUTINE_YIELD); 163 } 164 165 bool qemu_coroutine_entered(Coroutine *co) 166 { 167 return co->caller; 168 } 169