call ngx_localtime may cause deadlock?

georgexsh nginx-forum at
Thu Mar 4 13:09:33 MSK 2010

I am writing a module based on nginx 0.7.65, ngx_localtime() is called in the module.
Problem is, if set "timer_resolution  100ms;" in config file, nginx workers(*4) will hangs randomly. then if "timer_resolution" command was turned off , everything works just fine.

here is the backtrace (coredump generated with gcore(1) on a hanged worker process):

#0  0x007347a2 in ?? ()
#1  0x00823a9e in pthread_cond_init@@GLIBC_2.3.2 () from /lib/tls/
#2  0x007c942d in __wcsmbs_named_conv () from /lib/tls/
#3  0x080611c6 in ngx_localtime (s=1267569890, tm=0x9ba2048) at src/os/unix/ngx_time.c:59
#4  0x08055223 in ngx_time_update (sec=1267569890, msec=5) at src/core/ngx_times.c:114
#5  0x0805e51a in ngx_timer_signal_handler (signo=14) at src/event/ngx_event.c:565
#6  0x00775898 in __open_catalog () from /lib/tls/
#7  0x007cc043 in __tzfile_read () from /lib/tls/
#8  0x007cb217 in tzset_internal () from /lib/tls/
#9  0x007c942d in __wcsmbs_named_conv () from /lib/tls/
#10 0x080611c6 in ngx_localtime (s=1267569889, tm=0x875ff4) at src/os/unix/ngx_time.c:59
#11 0x08088c9f in ngx_foo_time_str (r=0x9dcdc28, time_str=0xbfe18450, t=-4) at ./ngx_foo_module//uti.c:111
#12 0x08087d1a in ngx_http_foo_record (r=0x9dcdc28, request_arg=0x9dcddb0) at ./ngx_foo_module//foo.c:124
#13 0x0808788c in ngx_http_foo_handler (r=0x9dcdc28) at ./ngx_foo_module//ngx_http_foo_module.c:74
#14 0x0806d4f9 in ngx_http_core_content_phase (r=0x9dcdc28, ph=0x9bb9938) at src/http/ngx_http_core_module.c:1262

strace shows  (not on the same worker, but similar) :

futex(0x2c2eec, FUTEX_WAIT, 2, NULL) 

I guess this situation is a deadlock, happens beneath localtime_r() of glibc.
While my module is calling localtime_r, a time update signal trigged localtime at the same time, then deadlocked. Is this correct?

Now I employ ngx_gmtime() to get formated time instead of ngx_localtime(), works stable for weeks. Maybe ngx_localtime() should not be used outside ngx_time_update().

Posted at Nginx Forum:,59851,59851#msg-59851

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