[Gluster-devel] glusterd stuck for glusterfs with version 3.12.15

Tue Apr 9 07:57:15 UTC 2019

Can you figure out some possible reason why iobref is corrupted, is it possible that thread 8 has called poll in and iobref has been relased, but the lock within it is not properly released (as I can not find any free lock operation in iobref_destroy), then thread 9 called rpc_transport_pollin_destroy again, and so stuck on this lock
Also, there should not be two thread handling the same socket at the same time, although there has been a patch claimed to tackle this issue.

cynthia

From: Raghavendra Gowdappa <rgowdapp at redhat.com>
Sent: Tuesday, April 09, 2019 3:52 PM
To: Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou at nokia-sbell.com>
Cc: gluster-devel at gluster.org
Subject: Re: glusterd stuck for glusterfs with version 3.12.15

On Mon, Apr 8, 2019 at 7:42 AM Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou at nokia-sbell.com<mailto:cynthia.zhou at nokia-sbell.com>> wrote:
Hi glusterfs experts,
Good day!
In my test env, sometimes glusterd stuck issue happened, and it is not responding to any gluster commands, when I checked this issue I find that glusterd thread 9 and thread 8 is dealing with the same socket, I thought following patch should be able to solve this issue, however after I merged this patch this issue still exist. When I looked into this code, it seems socket_event_poll_in called event_handled before rpc_transport_pollin_destroy, I think this gives the chance for another poll for the exactly the same socket. And caused this glusterd stuck issue, also, I find there is no   LOCK_DESTROY(&iobref->lock)
In iobref_destroy, I think it is better to add destroy lock.
Following is the gdb info when this issue happened, I would like to know your opinion on this issue, thanks!

SHA-1: f747d55a7fd364e2b9a74fe40360ab3cb7b11537

* socket: fix issue on concurrent handle of a socket

GDB INFO:
Thread 8 is blocked on pthread_cond_wait, and thread 9 is blocked in iobref_unref, I think
Thread 9 (Thread 0x7f9edf7fe700 (LWP 1933)):
#0  0x00007f9ee9fd785c in __lll_lock_wait () from /lib64/libpthread.so.0
#1  0x00007f9ee9fda657 in __lll_lock_elision () from /lib64/libpthread.so.0
#2  0x00007f9eeb24cae6 in iobref_unref (iobref=0x7f9ed00063b0) at iobuf.c:944
#3  0x00007f9eeafd2f29 in rpc_transport_pollin_destroy (pollin=0x7f9ed00452d0) at rpc-transport.c:123
#4  0x00007f9ee4fbf319 in socket_event_poll_in (this=0x7f9ed0049cc0, notify_handled=_gf_true) at socket.c:2322
#5  0x00007f9ee4fbf932 in socket_event_handler (fd=36, idx=27, gen=4, data=0x7f9ed0049cc0, poll_in=1, poll_out=0, poll_err=0) at socket.c:2471
#6  0x00007f9eeb2825d4 in event_dispatch_epoll_handler (event_pool=0x17feb00, event=0x7f9edf7fde84) at event-epoll.c:583
#7  0x00007f9eeb2828ab in event_dispatch_epoll_worker (data=0x180d0c0) at event-epoll.c:659
#8  0x00007f9ee9fce5da in start_thread () from /lib64/libpthread.so.0
#9  0x00007f9ee98a4eaf in clone () from /lib64/libc.so.6

Thread 8 (Thread 0x7f9edffff700 (LWP 1932)):
#0  0x00007f9ee9fd785c in __lll_lock_wait () from /lib64/libpthread.so.0
#1  0x00007f9ee9fd2b42 in __pthread_mutex_cond_lock () from /lib64/libpthread.so.0
#2  0x00007f9ee9fd44a8 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#3  0x00007f9ee4fbadab in socket_event_poll_err (this=0x7f9ed0049cc0, gen=4, idx=27) at socket.c:1201
#4  0x00007f9ee4fbf99c in socket_event_handler (fd=36, idx=27, gen=4, data=0x7f9ed0049cc0, poll_in=1, poll_out=0, poll_err=0) at socket.c:2480
#5  0x00007f9eeb2825d4 in event_dispatch_epoll_handler (event_pool=0x17feb00, event=0x7f9edfffee84) at event-epoll.c:583
#6  0x00007f9eeb2828ab in event_dispatch_epoll_worker (data=0x180cf20) at event-epoll.c:659
#7  0x00007f9ee9fce5da in start_thread () from /lib64/libpthread.so.0
#8  0x00007f9ee98a4eaf in clone () from /lib64/libc.so.6

(gdb) thread 9
[Switching to thread 9 (Thread 0x7f9edf7fe700 (LWP 1933))]
#0  0x00007f9ee9fd785c in __lll_lock_wait () from /lib64/libpthread.so.0
(gdb) bt
#0  0x00007f9ee9fd785c in __lll_lock_wait () from /lib64/libpthread.so.0
#1  0x00007f9ee9fda657 in __lll_lock_elision () from /lib64/libpthread.so.0
#2  0x00007f9eeb24cae6 in iobref_unref (iobref=0x7f9ed00063b0) at iobuf.c:944
#3  0x00007f9eeafd2f29 in rpc_transport_pollin_destroy (pollin=0x7f9ed00452d0) at rpc-transport.c:123
#4  0x00007f9ee4fbf319 in socket_event_poll_in (this=0x7f9ed0049cc0, notify_handled=_gf_true) at socket.c:2322
#5  0x00007f9ee4fbf932 in socket_event_handler (fd=36, idx=27, gen=4, data=0x7f9ed0049cc0, poll_in=1, poll_out=0, poll_err=0) at socket.c:2471
#6  0x00007f9eeb2825d4 in event_dispatch_epoll_handler (event_pool=0x17feb00, event=0x7f9edf7fde84) at event-epoll.c:583
#7  0x00007f9eeb2828ab in event_dispatch_epoll_worker (data=0x180d0c0) at event-epoll.c:659
#8  0x00007f9ee9fce5da in start_thread () from /lib64/libpthread.so.0
#9  0x00007f9ee98a4eaf in clone () from /lib64/libc.so.6
(gdb) frame 2
#2  0x00007f9eeb24cae6 in iobref_unref (iobref=0x7f9ed00063b0) at iobuf.c:944
944 iobuf.c: No such file or directory.
(gdb) print *iobref
$1 = {lock = {spinlock = 2, mutex = {__data = {__lock = 2, __count = 222, __owner = -2120437760, __nusers = 1, __kind = 8960, __spins = 512,
        __elision = 0, __list = {__prev = 0x4000, __next = 0x7f9ed00063b000}},
      __size = "\002\000\000\000\336\000\000\000\000\260\234\201\001\000\000\000\000#\000\000\000\002\000\000\000@\000\000\000\000\000\000\000\260c\000О\177", __align = 953482739714}}, ref = -256, iobrefs = 0xffffffffffffffff, alloced = -1, used = -1}

looks like the iobref is corrupted here. It seems to be a use-after-free issue. We need to dig into why a freed iobref is being accessed here.

(gdb) quit
A debugging session is active.
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