* [Qemu-devel] 9pfs is broken in 2.5 (SIGSEGV) (bisected)
@ 2015-12-19 8:05 Michael Tokarev
2015-12-19 8:15 ` Michael Tokarev
[not found] ` <5675120F.3000904@tls.msk.ru>
0 siblings, 2 replies; 4+ messages in thread
From: Michael Tokarev @ 2015-12-19 8:05 UTC (permalink / raw)
To: qemu-devel; +Cc: Paolo Bonzini, Aneesh Kumar K.V, Greg Kurz
When trying to mount a 9p filesystem in guest in 2.5 qemu,
qemu immediately segfaults.
qemu-system-x86_64 ...
-fsdev local,security_model=none,id=fsd0,path=/tmp
-device virtio-9p-pci,fsdev=fsd0,mount_tag=fsd0
mount -t 9p -o trans=virtio,version=9p2000.u fsd0 /mnt
(SIGSEGV)
The problem goes down to the following commit:
commit ebac1202c95a4f1b76b6ef3f0f63926fa76e753e
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri Nov 27 12:43:06 2015 +0100
virtio-9p: use QEMU thread pool
The QEMU thread pool already has a mechanism to invoke callbacks in the main
thread. It does not need an EventNotifier and it is more efficient too.
Use it instead of GAsyncQueue + GThreadPool + glue.
As a side effect, it silences Coverity's complaint about an unchecked
return value for event_notifier_init.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
(removed no more needed #include <glib.h> from virtio-9p-coth.h)
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
This is a heads-up for now, digging further.
/mjt
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [Qemu-devel] 9pfs is broken in 2.5 (SIGSEGV) (bisected) 2015-12-19 8:05 [Qemu-devel] 9pfs is broken in 2.5 (SIGSEGV) (bisected) Michael Tokarev @ 2015-12-19 8:15 ` Michael Tokarev [not found] ` <5675120F.3000904@tls.msk.ru> 1 sibling, 0 replies; 4+ messages in thread From: Michael Tokarev @ 2015-12-19 8:15 UTC (permalink / raw) To: qemu-devel; +Cc: Paolo Bonzini, Aneesh Kumar K.V, Greg Kurz 19.12.2015 11:05, Michael Tokarev wrote: > commit ebac1202c95a4f1b76b6ef3f0f63926fa76e753e > Author: Paolo Bonzini <pbonzini@redhat.com> > Date: Fri Nov 27 12:43:06 2015 +0100 > virtio-9p: use QEMU thread pool Program received signal SIGSEGV, Segmentation fault. thread_pool_submit_aio (pool=0x0, func=0x55555580f6a0 <coroutine_enter_func>, arg=0x555557698870, cb=<optimized out>, opaque=<optimized out>) at /build/kvm/git/thread-pool.c:246 246 QLIST_INSERT_HEAD(&pool->head, req, all); (gdb) bt #0 thread_pool_submit_aio (pool=0x0, func=0x55555580f6a0 <coroutine_enter_func>, arg=0x555557698870, cb=<optimized out>, opaque=<optimized out>) at /build/kvm/git/thread-pool.c:246 #1 0x000055555592c9ed in aio_bh_call (bh=<optimized out>) at /build/kvm/git/async.c:64 #2 aio_bh_poll (ctx=ctx@entry=0x5555563c9360) at /build/kvm/git/async.c:92 #3 0x0000555555939390 in aio_dispatch (ctx=0x5555563c9360) at /build/kvm/git/aio-posix.c:305 #4 0x000055555592c7de in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at /build/kvm/git/async.c:231 #5 0x00007ffff49d1c5d in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0 #6 0x0000555555937cf8 in glib_pollfds_poll () at /build/kvm/git/main-loop.c:211 #7 os_host_main_loop_wait (timeout=<optimized out>) at /build/kvm/git/main-loop.c:256 #8 main_loop_wait (nonblocking=<optimized out>) at /build/kvm/git/main-loop.c:504 #9 0x00005555556dbe3e in main_loop () at /build/kvm/git/vl.c:1923 #10 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at /build/kvm/git/vl.c:4684 (gdb) p pool $2 = (ThreadPool *) 0x0 Woops. /mjt ^ permalink raw reply [flat|nested] 4+ messages in thread
[parent not found: <5675120F.3000904@tls.msk.ru>]
* Re: [Qemu-devel] 9pfs is broken in 2.5 (SIGSEGV) (bisected) [not found] ` <5675120F.3000904@tls.msk.ru> @ 2015-12-19 9:16 ` Michael Tokarev 2015-12-19 18:41 ` Greg Kurz 0 siblings, 1 reply; 4+ messages in thread From: Michael Tokarev @ 2015-12-19 9:16 UTC (permalink / raw) To: qemu-devel; +Cc: Paolo Bonzini, Aneesh Kumar K.V, Greg Kurz 19.12.2015 11:15, Michael Tokarev wrote: >> commit ebac1202c95a4f1b76b6ef3f0f63926fa76e753e >> Author: Paolo Bonzini <pbonzini@redhat.com> >> Date: Fri Nov 27 12:43:06 2015 +0100 >> virtio-9p: use QEMU thread pool > > Program received signal SIGSEGV, Segmentation fault. > thread_pool_submit_aio (pool=0x0, func=0x55555580f6a0 <coroutine_enter_func>, arg=0x555557698870, cb=<optimized out>, > opaque=<optimized out>) at /build/kvm/git/thread-pool.c:246 > 246 QLIST_INSERT_HEAD(&pool->head, req, all); > (gdb) bt > #0 thread_pool_submit_aio (pool=0x0, func=0x55555580f6a0 <coroutine_enter_func>, arg=0x555557698870, cb=<optimized out>, > opaque=<optimized out>) at /build/kvm/git/thread-pool.c:246 > #1 0x000055555592c9ed in aio_bh_call (bh=<optimized out>) at /build/kvm/git/async.c:64 > #2 aio_bh_poll (ctx=ctx@entry=0x5555563c9360) at /build/kvm/git/async.c:92 > #3 0x0000555555939390 in aio_dispatch (ctx=0x5555563c9360) at /build/kvm/git/aio-posix.c:305 > #4 0x000055555592c7de in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) > at /build/kvm/git/async.c:231 > #5 0x00007ffff49d1c5d in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0 > #6 0x0000555555937cf8 in glib_pollfds_poll () at /build/kvm/git/main-loop.c:211 > #7 os_host_main_loop_wait (timeout=<optimized out>) at /build/kvm/git/main-loop.c:256 > #8 main_loop_wait (nonblocking=<optimized out>) at /build/kvm/git/main-loop.c:504 > #9 0x00005555556dbe3e in main_loop () at /build/kvm/git/vl.c:1923 > #10 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at /build/kvm/git/vl.c:4684 > (gdb) p pool > $2 = (ThreadPool *) 0x0 In 9pfs/virtio-9p-coth.c:co_run_in_worker_bh(), in this context: void co_run_in_worker_bh(void *opaque) { Coroutine *co = opaque; thread_pool_submit_aio(qemu_get_aio_context()->thread_pool, coroutine_enter_func, co, coroutine_enter_cb, co); } qemu_get_aio_context()->thread_pool is NULL. Thanks, /mjt ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] 9pfs is broken in 2.5 (SIGSEGV) (bisected) 2015-12-19 9:16 ` Michael Tokarev @ 2015-12-19 18:41 ` Greg Kurz 0 siblings, 0 replies; 4+ messages in thread From: Greg Kurz @ 2015-12-19 18:41 UTC (permalink / raw) To: Michael Tokarev; +Cc: Paolo Bonzini, qemu-devel, Aneesh Kumar K.V On Sat, 19 Dec 2015 12:16:58 +0300 Michael Tokarev <mjt@tls.msk.ru> wrote: > 19.12.2015 11:15, Michael Tokarev wrote: > >> commit ebac1202c95a4f1b76b6ef3f0f63926fa76e753e > >> Author: Paolo Bonzini <pbonzini@redhat.com> > >> Date: Fri Nov 27 12:43:06 2015 +0100 > >> virtio-9p: use QEMU thread pool > > > > Program received signal SIGSEGV, Segmentation fault. > > thread_pool_submit_aio (pool=0x0, func=0x55555580f6a0 <coroutine_enter_func>, arg=0x555557698870, cb=<optimized out>, > > opaque=<optimized out>) at /build/kvm/git/thread-pool.c:246 > > 246 QLIST_INSERT_HEAD(&pool->head, req, all); > > (gdb) bt > > #0 thread_pool_submit_aio (pool=0x0, func=0x55555580f6a0 <coroutine_enter_func>, arg=0x555557698870, cb=<optimized out>, > > opaque=<optimized out>) at /build/kvm/git/thread-pool.c:246 > > #1 0x000055555592c9ed in aio_bh_call (bh=<optimized out>) at /build/kvm/git/async.c:64 > > #2 aio_bh_poll (ctx=ctx@entry=0x5555563c9360) at /build/kvm/git/async.c:92 > > #3 0x0000555555939390 in aio_dispatch (ctx=0x5555563c9360) at /build/kvm/git/aio-posix.c:305 > > #4 0x000055555592c7de in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) > > at /build/kvm/git/async.c:231 > > #5 0x00007ffff49d1c5d in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0 > > #6 0x0000555555937cf8 in glib_pollfds_poll () at /build/kvm/git/main-loop.c:211 > > #7 os_host_main_loop_wait (timeout=<optimized out>) at /build/kvm/git/main-loop.c:256 > > #8 main_loop_wait (nonblocking=<optimized out>) at /build/kvm/git/main-loop.c:504 > > #9 0x00005555556dbe3e in main_loop () at /build/kvm/git/vl.c:1923 > > #10 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at /build/kvm/git/vl.c:4684 > > (gdb) p pool > > $2 = (ThreadPool *) 0x0 > > In 9pfs/virtio-9p-coth.c:co_run_in_worker_bh(), in this context: > > void co_run_in_worker_bh(void *opaque) > { > Coroutine *co = opaque; > thread_pool_submit_aio(qemu_get_aio_context()->thread_pool, > coroutine_enter_func, co, coroutine_enter_cb, co); > } > > qemu_get_aio_context()->thread_pool is NULL. > > Thanks, > > /mjt > Hi Michael, It works-for-me-of-course on ppc64le and x86_64. I could verify with gdb that thread_pool gets set early: #0 aio_get_thread_pool (ctx=0x10e6b7a0) at /home/greg/Work/qemu/qemu-master/async.c:280 #1 0x00000000105e06fc in paio_submit (bs=0x10e8d1c0, fd=15, sector_num=0, qiov=0x3fffffffe0e0, nb_sectors=1, cb=0x105f03e0 <bdrv_co_io_em_complete>, opaque=0x3fffb6e2fc88, type=1) at /home/greg/Work/qemu/qemu-master/block/raw-posix.c:1309 #2 0x00000000105e08a0 in raw_aio_submit (bs=0x10e8d1c0, sector_num=0, qiov=0x3fffffffe0e0, nb_sectors=1, cb=0x105f03e0 <bdrv_co_io_em_complete>, opaque=0x3fffb6e2fc88, type=1) at /home/greg/Work/qemu/qemu-master/block/raw-posix.c:1339 #3 0x00000000105e0a98 in raw_aio_readv (bs=0x10e8d1c0, sector_num=0, qiov=0x3fffffffe0e0, nb_sectors=1, cb=0x105f03e0 <bdrv_co_io_em_complete>, opaque=0x3fffb6e2fc88) at /home/greg/Work/qemu/qemu-master/block/raw-posix.c:1377 #4 0x00000000105f055c in bdrv_co_io_em (bs=0x10e8d1c0, sector_num=0, nb_sectors=1, iov=0x3fffffffe0e0, is_write=false) at /home/greg/Work/qemu/qemu-master/block/io.c:2300 #5 0x00000000105f0648 in bdrv_co_readv_em (bs=0x10e8d1c0, sector_num=0, nb_sectors=1, iov=0x3fffffffe0e0) at /home/greg/Work/qemu/qemu-master/block/io.c:2317 #6 0x00000000105eba90 in bdrv_aligned_preadv (bs=0x10e8d1c0, req=0x3fffb6e2fe48, offset=0, bytes=512, align=512, qiov=0x3fffffffe0e0, flags=0) at /home/greg/Work/qemu/qemu-master/block/io.c:900 #7 0x00000000105ebfd4 in bdrv_co_do_preadv (bs=0x10e8d1c0, offset=0, bytes=512, qiov=0x3fffffffe0e0, flags=(unknown: 0)) at /home/greg/Work/qemu/qemu-master/block/io.c:992 #8 0x00000000105eaa28 in bdrv_rw_co_entry (opaque=0x3fffffffe040) at /home/greg/Work/qemu/qemu-master/block/io.c:534 #9 0x0000000010675bc4 in coroutine_trampoline (i0=283706576, i1=0) at /home/greg/Work/qemu/qemu-master/util/coroutine-ucontext.c:80 #10 0x00003fffb76c1c4c in makecontext () from /lib64/power8/libc.so.6 Probably other options on the command line make the difference. Anyway it would seem we can reach co_run_in_worker_bh() without the main thread pool being initialized... I'll work this out early next week. Thanks. -- Greg ^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-12-19 8:05 [Qemu-devel] 9pfs is broken in 2.5 (SIGSEGV) (bisected) Michael Tokarev
2015-12-19 8:15 ` Michael Tokarev
[not found] ` <5675120F.3000904@tls.msk.ru>
2015-12-19 9:16 ` Michael Tokarev
2015-12-19 18:41 ` Greg Kurz
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