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author | Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp> | 2009-05-15 17:30:24 +0900 |
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committer | Dhaval Giani <dhaval@linux.vnet.ibm.com> | 2009-05-22 14:46:21 +0530 |
commit | 70111cd03653c3ceab9d907c14fa35e5881b2735 (patch) | |
tree | caa124d519382cd8cb82eaef65f19ffa06c76423 /src/daemon | |
parent | 781e12c79e97f76799af8c557c6e96c508e645df (diff) | |
download | libcg-70111cd03653c3ceab9d907c14fa35e5881b2735.tar.gz libcg-70111cd03653c3ceab9d907c14fa35e5881b2735.tar.xz libcg-70111cd03653c3ceab9d907c14fa35e5881b2735.zip |
Fix the deadlock of vsyslog() call.
Hi,
I found the deadlock problem that a cgrulesengd daemon stalls if
service "cgred" is reloaded while many UID events happen.
The following is the gdb output by attaching the stalling daemon:
(gdb) bt
#0 0x0000003b298dd918 in __lll_mutex_lock_wait () from /lib64/libc.so.6
#1 0x0000003b298ce847 in _L_lock_646 () from /lib64/libc.so.6
#2 0x0000003b298ce2da in __vsyslog_chk () from /lib64/libc.so.6
#3 0x0000000000401533 in flog (level=5, format=0x402778 "Reloading rules configuration.") at cgrule sengd.c:130
#4 0x00000000004015d1 in cgre_flash_rules (signum=<value optimized out>) at cgrulesengd.c:644
#5 <signal handler called>
#6 0x0000003b298d27b5 in send () from /lib64/libc.so.6
#7 0x0000003b298ce3a0 in __vsyslog_chk () from /lib64/libc.so.6
#8 0x0000000000401533 in flog (level=4, format=0x402b82 "Failed to open %s") at cgrulesengd.c:130
#9 0x0000000000401cc7 in cgre_process_event (ev=0x7fff8ad11cc4, type=4) at cgrulesengd.c:161
#10 0x0000000000401fd5 in cgre_create_netlink_socket_process_msg () at cgrulesengd.c:486
#11 0x00000000004023ca in main (argc=1, argv=<value optimized out>) at cgrulesengd.c:878
(gdb)
We can see __vsyslog_chk() is called twice, because the daemon
recieved a SIGUSR2 signal in __vsyslog_chk(). In __vsyslog_chk(),
"syslog_lock" is locked by __libc_lock_lock(syslog_lock).
So I think vsyslog() should be protected by blocking the signal,
and this patch fixes the problem by doing it.
Thanks
Ken'ichi Ohmichi
Signed-off-by: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Diffstat (limited to 'src/daemon')
-rw-r--r-- | src/daemon/cgrulesengd.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/daemon/cgrulesengd.c b/src/daemon/cgrulesengd.c index c025862..1a61476 100644 --- a/src/daemon/cgrulesengd.c +++ b/src/daemon/cgrulesengd.c @@ -126,9 +126,17 @@ void flog(int level, const char *format, ...) } if (logfacility) { + sigset_t sigset; + + sigemptyset(&sigset); + sigaddset(&sigset, SIGUSR2); + sigprocmask(SIG_BLOCK, &sigset, NULL); + va_start(ap, format); vsyslog(LOG_MAKEPRI(logfacility, level), format, ap); va_end(ap); + + sigprocmask(SIG_UNBLOCK, &sigset, NULL); } } |