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/thread.h" 18 #include "qemu/atomic.h" 19 #include "qemu/coroutine.h" 20 #include "qemu/coroutine_int.h" 21 #include "qemu/coroutine-tls.h" 22 #include "block/aio.h" 23 24 /** Initial batch size is 64, and is increased on demand */ 25 enum { 26 POOL_INITIAL_BATCH_SIZE = 64, 27 }; 28 29 /** Free list to speed up creation */ 30 static QSLIST_HEAD(, Coroutine) release_pool = QSLIST_HEAD_INITIALIZER(pool); 31 static unsigned int pool_batch_size = POOL_INITIAL_BATCH_SIZE; 32 static unsigned int release_pool_size; 33 34 typedef QSLIST_HEAD(, Coroutine) CoroutineQSList; 35 QEMU_DEFINE_STATIC_CO_TLS(CoroutineQSList, alloc_pool); 36 QEMU_DEFINE_STATIC_CO_TLS(unsigned int, alloc_pool_size); 37 QEMU_DEFINE_STATIC_CO_TLS(Notifier, coroutine_pool_cleanup_notifier); 38 39 static void coroutine_pool_cleanup(Notifier *n, void *value) 40 { 41 Coroutine *co; 42 Coroutine *tmp; 43 CoroutineQSList *alloc_pool = get_ptr_alloc_pool(); 44 45 QSLIST_FOREACH_SAFE(co, alloc_pool, pool_next, tmp) { 46 QSLIST_REMOVE_HEAD(alloc_pool, pool_next); 47 qemu_coroutine_delete(co); 48 } 49 } 50 51 Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque) 52 { 53 Coroutine *co = NULL; 54 55 if (CONFIG_COROUTINE_POOL) { 56 CoroutineQSList *alloc_pool = get_ptr_alloc_pool(); 57 58 co = QSLIST_FIRST(alloc_pool); 59 if (!co) { 60 if (release_pool_size > qatomic_read(&pool_batch_size)) { 61 /* Slow path; a good place to register the destructor, too. */ 62 Notifier *notifier = get_ptr_coroutine_pool_cleanup_notifier(); 63 if (!notifier->notify) { 64 notifier->notify = coroutine_pool_cleanup; 65 qemu_thread_atexit_add(notifier); 66 } 67 68 /* This is not exact; there could be a little skew between 69 * release_pool_size and the actual size of release_pool. But 70 * it is just a heuristic, it does not need to be perfect. 71 */ 72 set_alloc_pool_size(qatomic_xchg(&release_pool_size, 0)); 73 QSLIST_MOVE_ATOMIC(alloc_pool, &release_pool); 74 co = QSLIST_FIRST(alloc_pool); 75 } 76 } 77 if (co) { 78 QSLIST_REMOVE_HEAD(alloc_pool, pool_next); 79 set_alloc_pool_size(get_alloc_pool_size() - 1); 80 } 81 } 82 83 if (!co) { 84 co = qemu_coroutine_new(); 85 } 86 87 co->entry = entry; 88 co->entry_arg = opaque; 89 QSIMPLEQ_INIT(&co->co_queue_wakeup); 90 return co; 91 } 92 93 static void coroutine_delete(Coroutine *co) 94 { 95 co->caller = NULL; 96 97 if (CONFIG_COROUTINE_POOL) { 98 if (release_pool_size < qatomic_read(&pool_batch_size) * 2) { 99 QSLIST_INSERT_HEAD_ATOMIC(&release_pool, co, pool_next); 100 qatomic_inc(&release_pool_size); 101 return; 102 } 103 if (get_alloc_pool_size() < qatomic_read(&pool_batch_size)) { 104 QSLIST_INSERT_HEAD(get_ptr_alloc_pool(), co, pool_next); 105 set_alloc_pool_size(get_alloc_pool_size() + 1); 106 return; 107 } 108 } 109 110 qemu_coroutine_delete(co); 111 } 112 113 void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co) 114 { 115 QSIMPLEQ_HEAD(, Coroutine) pending = QSIMPLEQ_HEAD_INITIALIZER(pending); 116 Coroutine *from = qemu_coroutine_self(); 117 118 QSIMPLEQ_INSERT_TAIL(&pending, co, co_queue_next); 119 120 /* Run co and any queued coroutines */ 121 while (!QSIMPLEQ_EMPTY(&pending)) { 122 Coroutine *to = QSIMPLEQ_FIRST(&pending); 123 CoroutineAction ret; 124 125 /* Cannot rely on the read barrier for to in aio_co_wake(), as there are 126 * callers outside of aio_co_wake() */ 127 const char *scheduled = qatomic_mb_read(&to->scheduled); 128 129 QSIMPLEQ_REMOVE_HEAD(&pending, co_queue_next); 130 131 trace_qemu_aio_coroutine_enter(ctx, from, to, to->entry_arg); 132 133 /* if the Coroutine has already been scheduled, entering it again will 134 * cause us to enter it twice, potentially even after the coroutine has 135 * been deleted */ 136 if (scheduled) { 137 fprintf(stderr, 138 "%s: Co-routine was already scheduled in '%s'\n", 139 __func__, scheduled); 140 abort(); 141 } 142 143 if (to->caller) { 144 fprintf(stderr, "Co-routine re-entered recursively\n"); 145 abort(); 146 } 147 148 to->caller = from; 149 to->ctx = ctx; 150 151 /* Store to->ctx before anything that stores to. Matches 152 * barrier in aio_co_wake and qemu_co_mutex_wake. 153 */ 154 smp_wmb(); 155 156 ret = qemu_coroutine_switch(from, to, COROUTINE_ENTER); 157 158 /* Queued coroutines are run depth-first; previously pending coroutines 159 * run after those queued more recently. 160 */ 161 QSIMPLEQ_PREPEND(&pending, &to->co_queue_wakeup); 162 163 switch (ret) { 164 case COROUTINE_YIELD: 165 break; 166 case COROUTINE_TERMINATE: 167 assert(!to->locks_held); 168 trace_qemu_coroutine_terminate(to); 169 coroutine_delete(to); 170 break; 171 default: 172 abort(); 173 } 174 } 175 } 176 177 void qemu_coroutine_enter(Coroutine *co) 178 { 179 qemu_aio_coroutine_enter(qemu_get_current_aio_context(), co); 180 } 181 182 void qemu_coroutine_enter_if_inactive(Coroutine *co) 183 { 184 if (!qemu_coroutine_entered(co)) { 185 qemu_coroutine_enter(co); 186 } 187 } 188 189 void coroutine_fn qemu_coroutine_yield(void) 190 { 191 Coroutine *self = qemu_coroutine_self(); 192 Coroutine *to = self->caller; 193 194 trace_qemu_coroutine_yield(self, to); 195 196 if (!to) { 197 fprintf(stderr, "Co-routine is yielding to no one\n"); 198 abort(); 199 } 200 201 self->caller = NULL; 202 qemu_coroutine_switch(self, to, COROUTINE_YIELD); 203 } 204 205 bool qemu_coroutine_entered(Coroutine *co) 206 { 207 return co->caller; 208 } 209 210 AioContext *coroutine_fn qemu_coroutine_get_aio_context(Coroutine *co) 211 { 212 return co->ctx; 213 } 214 215 void qemu_coroutine_increase_pool_batch_size(unsigned int additional_pool_size) 216 { 217 qatomic_add(&pool_batch_size, additional_pool_size); 218 } 219 220 void qemu_coroutine_decrease_pool_batch_size(unsigned int removing_pool_size) 221 { 222 qatomic_sub(&pool_batch_size, removing_pool_size); 223 } 224