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block/nbd: safer transition to receiving request

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req->receiving is a flag of request being in one concrete yield point
in nbd_co_do_receive_one_chunk().

Such kind of boolean flag is always better to unset before scheduling
the coroutine, to avoid double scheduling. So, let's be more careful.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-33-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2021-06-10 13:08:02 +03:00 committed by Eric Blake
parent 91e0998f5a
commit bbfb7c2f35
1 changed files with 3 additions and 1 deletions
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block/nbd.c
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@ -150,6 +150,7 @@ static void nbd_recv_coroutines_wake_all(BDRVNBDState *s)
NBDClientRequest *req = &s->requests[i]; NBDClientRequest *req = &s->requests[i];
if (req->coroutine && req->receiving) { if (req->coroutine && req->receiving) {
req->receiving = false;
aio_co_wake(req->coroutine); aio_co_wake(req->coroutine);
} }
} }
@ -548,6 +549,7 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
* connection_co happens through a bottom half, which can only * connection_co happens through a bottom half, which can only
* run after we yield. * run after we yield.
*/ */
s->requests[i].receiving = false;
aio_co_wake(s->requests[i].coroutine); aio_co_wake(s->requests[i].coroutine);
qemu_coroutine_yield(); qemu_coroutine_yield();
} }
@ -934,7 +936,7 @@ static coroutine_fn int nbd_co_do_receive_one_chunk(
/* Wait until we're woken up by nbd_connection_entry. */ /* Wait until we're woken up by nbd_connection_entry. */
s->requests[i].receiving = true; s->requests[i].receiving = true;
qemu_coroutine_yield(); qemu_coroutine_yield();
s->requests[i].receiving = false; assert(!s->requests[i].receiving);
if (!nbd_client_connected(s)) { if (!nbd_client_connected(s)) {
error_setg(errp, "Connection closed"); error_setg(errp, "Connection closed");
return -EIO; return -EIO;