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coroutine: protect global pool with a mutex

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The coroutine freelist is a global pool of unused coroutines.  It avoids
the setup/teardown overhead associated with the coroutine lifecycle.
Since the pool is global, we need to synchronize access so that
coroutines can be used outside the BQL.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-05-17 15:51:25 +02:00
parent bd91ecbf5b
commit b84c458623
1 changed files with 18 additions and 2 deletions
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20
qemu-coroutine.c
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@ -14,6 +14,7 @@
#include "trace.h"
#include "qemu-common.h"
#include "qemu/thread.h"
#include "block/coroutine.h"
#include "block/coroutine_int.h"
@ -23,6 +24,7 @@ enum {
};
/** Free list to speed up creation */
static QemuMutex pool_lock;
static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
static unsigned int pool_size;
@ -30,11 +32,15 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
{
Coroutine *co;
qemu_mutex_lock(&pool_lock);
co = QSLIST_FIRST(&pool);
if (co) {
QSLIST_REMOVE_HEAD(&pool, pool_next);
pool_size--;
} else {
}
qemu_mutex_unlock(&pool_lock);
if (!co) {
co = qemu_coroutine_new();
}
@ -44,17 +50,25 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
static void coroutine_delete(Coroutine *co)
{
qemu_mutex_lock(&pool_lock);
if (pool_size < POOL_MAX_SIZE) {
QSLIST_INSERT_HEAD(&pool, co, pool_next);
co->caller = NULL;
pool_size++;
qemu_mutex_unlock(&pool_lock);
return;
}
qemu_mutex_unlock(&pool_lock);
qemu_coroutine_delete(co);
}
static void __attribute__((destructor)) coroutine_cleanup(void)
static void __attribute__((constructor)) coroutine_pool_init(void)
{
qemu_mutex_init(&pool_lock);
}
static void __attribute__((destructor)) coroutine_pool_cleanup(void)
{
Coroutine *co;
Coroutine *tmp;
@ -63,6 +77,8 @@ static void __attribute__((destructor)) coroutine_cleanup(void)
QSLIST_REMOVE_HEAD(&pool, pool_next);
qemu_coroutine_delete(co);
}
qemu_mutex_destroy(&pool_lock);
}
static void coroutine_swap(Coroutine *from, Coroutine *to)