On Fri, May 15, 2009 at 05:30:24PM +0900, Ken'ichi Ohmichi wrote:
>
> 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 <[email protected]>
thanks, applied.
> ---
> 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);
> }
> }
>
>
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--
regards,
Dhaval
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