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/libc.so.6 #2 0x007c942d in __wcsmbs_named_conv () from /lib/tls/libc.so.6 #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/libc.so.6 #7 0x007cc043 in __tzfile_read () from /lib/tls/libc.so.6 #8 0x007cb217 in tzset_internal () from /lib/tls/libc.so.6 #9 0x007c942d in __wcsmbs_named_conv () from /lib/tls/libc.so.6 #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: http://forum.nginx.org/read.php?2,59851,59851#msg-59851