主线程在写 syslog,同时在信号处理函数中也在写syslog,当主线程在写的时候，如果同时触发了信号，那么将会导致死锁。
$pstack 4289
#0 0x00000036768df9ee in __lll_lock_wait_private () from /lib64/libc.so.6
#1 0x000000367688d0dd in _L_lock_1685 () from /lib64/libc.so.6
#2 0x000000367688ce27 in __tz_convert () from /lib64/libc.so.6
#3 0x00000036768cff7d in __vsyslog_chk () from /lib64/libc.so.6
#4 0x00000036768d0580 in syslog () from /lib64/libc.so.6
#5 0x00000000004c8c81 in SigChldHandler ()
#6
#7 0x000000367688d2ad in __tzfile_compute () from /lib64/libc.so.6
#8 0x000000367688ce5f in __tz_convert () from /lib64/libc.so.6
#9 0x00000036768cff7d in __vsyslog_chk () from /lib64/libc.so.6
#10 0x00000036768d0580 in syslog () from /lib64/libc.so.6
$pstack 4289
#0 0x00000036768df9ee in __lll_lock_wait_private () from /lib64/libc.so.6
#1 0x000000367688d0dd in _L_lock_1685 () from /lib64/libc.so.6
#2 0x000000367688ce27 in __tz_convert () from /lib64/libc.so.6
#3 0x00000036768cff7d in __vsyslog_chk () from /lib64/libc.so.6
#4 0x00000036768d0580 in syslog () from /lib64/libc.so.6
#5 0x00000000004c8c81 in SigChldHandler ()
#6
#7 0x000000367688d2ad in __tzfile_compute () from /lib64/libc.so.6
#8 0x000000367688ce5f in __tz_convert () from /lib64/libc.so.6
#9 0x00000036768cff7d in __vsyslog_chk () from /lib64/libc.so.6
#10 0x00000036768d0580 in syslog () from /lib64/libc.so.6
#11 0x00000000004c5c21 in HandleNewBinRequest ()
根本原因是syslog内部会调用malloc，而malloc是不可重入函数，在信号处理函数中调用不可重入函数会导致死锁问题。
