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co-shared-resource: protect with a mutex 

co-shared-resource is currently not thread-safe, as also reported
in co-shared-resource.h. Add a QemuMutex because co_try_get_from_shres
can also be invoked from non-coroutine context.

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210614081130.22134-6-eesposit@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2021-06-14 10:11:30 +02:00 committed by Vladimir Sementsov-Ogievskiy
parent a7b4f8fc09
commit 55fa54a789
2 changed files with 20 additions and 8 deletions
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4
include/qemu/co-shared-resource.h
View File

@ -26,15 +26,13 @@
#ifndef QEMU_CO_SHARED_RESOURCE_H
#define QEMU_CO_SHARED_RESOURCE_H
/* Accesses to co-shared-resource API are thread-safe */
typedef struct SharedResource SharedResource;
/*
* Create SharedResource structure
*
* @total: total amount of some resource to be shared between clients
*
* Note: this API is not thread-safe.
*/
SharedResource *shres_create(uint64_t total);

24
util/qemu-co-shared-resource.c
View File

@ -28,10 +28,13 @@
#include "qemu/co-shared-resource.h"
struct SharedResource {
uint64_t total;
uint64_t available;
uint64_t total; /* Set in shres_create() and not changed anymore */
/* State fields protected by lock */
uint64_t available;
CoQueue queue;
QemuMutex lock;
};
SharedResource *shres_create(uint64_t total)
@ -40,6 +43,7 @@ SharedResource *shres_create(uint64_t total)
s->total = s->available = total;
qemu_co_queue_init(&s->queue);
qemu_mutex_init(&s->lock);
return s;
}
@ -47,10 +51,12 @@ SharedResource *shres_create(uint64_t total)
void shres_destroy(SharedResource *s)
{
assert(s->available == s->total);
qemu_mutex_destroy(&s->lock);
g_free(s);
}
bool co_try_get_from_shres(SharedResource *s, uint64_t n)
/* Called with lock held. */
static bool co_try_get_from_shres_locked(SharedResource *s, uint64_t n)
{
if (s->available >= n) {
s->available -= n;
@ -60,16 +66,24 @@ bool co_try_get_from_shres(SharedResource *s, uint64_t n)
return false;
}
bool co_try_get_from_shres(SharedResource *s, uint64_t n)
{
QEMU_LOCK_GUARD(&s->lock);
return co_try_get_from_shres_locked(s, n);
}
void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n)
{
assert(n <= s->total);
while (!co_try_get_from_shres(s, n)) {
qemu_co_queue_wait(&s->queue, NULL);
QEMU_LOCK_GUARD(&s->lock);
while (!co_try_get_from_shres_locked(s, n)) {
qemu_co_queue_wait(&s->queue, &s->lock);
}
}
void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n)
{
QEMU_LOCK_GUARD(&s->lock);
assert(s->total - s->available >= n);
s->available += n;
qemu_co_queue_restart_all(&s->queue);