diff options
author | Bin Wu <wu.wubin@huawei.com> | 2015-02-10 15:20:46 +0800 |
---|---|---|
committer | Stefan Hajnoczi <stefanha@redhat.com> | 2015-02-16 15:07:17 +0000 |
commit | 141cabe6f144a1acb128186caf686f8fbde0a7e4 (patch) | |
tree | 992b80848ece9124100b25b25490b70d564a139b /block | |
parent | 81705ee4850b55ef4879c941e4a7703efd3cb760 (diff) | |
download | hqemu-141cabe6f144a1acb128186caf686f8fbde0a7e4.zip hqemu-141cabe6f144a1acb128186caf686f8fbde0a7e4.tar.gz |
nbd: fix the co_queue multi-adding bug
When we tested the VM migartion between different hosts with NBD
devices, we found if we sent a cancel command after the drive_mirror
was just started, a coroutine re-enter error would occur. The stack
was as follow:
(gdb) bt
00) 0x00007fdfc744d885 in raise () from /lib64/libc.so.6
01) 0x00007fdfc744ee61 in abort () from /lib64/libc.so.6
02) 0x00007fdfca467cc5 in qemu_coroutine_enter (co=0x7fdfcaedb400, opaque=0x0)
at qemu-coroutine.c:118
03) 0x00007fdfca467f6c in qemu_co_queue_run_restart (co=0x7fdfcaedb400) at
qemu-coroutine-lock.c:59
04) 0x00007fdfca467be5 in coroutine_swap (from=0x7fdfcaf3c4e8,
to=0x7fdfcaedb400) at qemu-coroutine.c:96
05) 0x00007fdfca467cea in qemu_coroutine_enter (co=0x7fdfcaedb400, opaque=0x0)
at qemu-coroutine.c:123
06) 0x00007fdfca467f6c in qemu_co_queue_run_restart (co=0x7fdfcaedbdc0) at
qemu-coroutine-lock.c:59
07) 0x00007fdfca467be5 in coroutine_swap (from=0x7fdfcaf3c4e8,
to=0x7fdfcaedbdc0) at qemu-coroutine.c:96
08) 0x00007fdfca467cea in qemu_coroutine_enter (co=0x7fdfcaedbdc0, opaque=0x0)
at qemu-coroutine.c:123
09) 0x00007fdfca4a1fa4 in nbd_recv_coroutines_enter_all (s=0x7fdfcaef7dd0) at
block/nbd-client.c:41
10) 0x00007fdfca4a1ff9 in nbd_teardown_connection (client=0x7fdfcaef7dd0) at
block/nbd-client.c:50
11) 0x00007fdfca4a20f0 in nbd_reply_ready (opaque=0x7fdfcaef7dd0) at
block/nbd-client.c:92
12) 0x00007fdfca45ed80 in aio_dispatch (ctx=0x7fdfcae15e90) at aio-posix.c:144
13) 0x00007fdfca45ef1b in aio_poll (ctx=0x7fdfcae15e90, blocking=false) at
aio-posix.c:222
14) 0x00007fdfca448c34 in aio_ctx_dispatch (source=0x7fdfcae15e90, callback=0x0,
user_data=0x0) at async.c:212
15) 0x00007fdfc8f2f69a in g_main_context_dispatch () from
/usr/lib64/libglib-2.0.so.0
16) 0x00007fdfca45c391 in glib_pollfds_poll () at main-loop.c:190
17) 0x00007fdfca45c489 in os_host_main_loop_wait (timeout=1483677098) at
main-loop.c:235
18) 0x00007fdfca45c57b in main_loop_wait (nonblocking=0) at main-loop.c:484
19) 0x00007fdfca25f403 in main_loop () at vl.c:2249
20) 0x00007fdfca266fc2 in main (argc=42, argv=0x7ffff517d638,
envp=0x7ffff517d790) at vl.c:4814
We find the nbd_recv_coroutines_enter_all function (triggered by a cancel
command or a network connection breaking down) will enter a coroutine which
is waiting for the sending lock. If the lock is still held by another coroutine,
the entering coroutine will be added into the co_queue again. Latter, when the
lock is released, a coroutine re-enter error will occur.
This bug can be fixed simply by delaying the setting of recv_coroutine as
suggested by paolo. After applying this patch, we have tested the cancel
operation in mirror phase looply for more than 5 hous and everything is fine.
Without this patch, a coroutine re-enter error will occur in 5 minutes.
Signed-off-by: Bn Wu <wu.wubin@huawei.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1423552846-3896-1-git-send-email-wu.wubin@huawei.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/nbd-client.c | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/block/nbd-client.c b/block/nbd-client.c index a01a37f..259f5a3 100644 --- a/block/nbd-client.c +++ b/block/nbd-client.c @@ -108,11 +108,22 @@ static int nbd_co_send_request(BlockDriverState *bs, { NbdClientSession *s = nbd_get_client_session(bs); AioContext *aio_context; - int rc, ret; + int rc, ret, i; qemu_co_mutex_lock(&s->send_mutex); + + for (i = 0; i < MAX_NBD_REQUESTS; i++) { + if (s->recv_coroutine[i] == NULL) { + s->recv_coroutine[i] = qemu_coroutine_self(); + break; + } + } + + assert(i < MAX_NBD_REQUESTS); + request->handle = INDEX_TO_HANDLE(s, i); s->send_coroutine = qemu_coroutine_self(); aio_context = bdrv_get_aio_context(bs); + aio_set_fd_handler(aio_context, s->sock, nbd_reply_ready, nbd_restart_write, bs); if (qiov) { @@ -168,8 +179,6 @@ static void nbd_co_receive_reply(NbdClientSession *s, static void nbd_coroutine_start(NbdClientSession *s, struct nbd_request *request) { - int i; - /* Poor man semaphore. The free_sema is locked when no other request * can be accepted, and unlocked after receiving one reply. */ if (s->in_flight >= MAX_NBD_REQUESTS - 1) { @@ -178,15 +187,7 @@ static void nbd_coroutine_start(NbdClientSession *s, } s->in_flight++; - for (i = 0; i < MAX_NBD_REQUESTS; i++) { - if (s->recv_coroutine[i] == NULL) { - s->recv_coroutine[i] = qemu_coroutine_self(); - break; - } - } - - assert(i < MAX_NBD_REQUESTS); - request->handle = INDEX_TO_HANDLE(s, i); + /* s->recv_coroutine[i] is set as soon as we get the send_lock. */ } static void nbd_coroutine_end(NbdClientSession *s, |