On 09.07.2013 19:30, Denys Vlasenko wrote: > On 07/09/2013 09:17 AM, Florian Kelbert wrote: >> >> >> On 08.07.2013 10:00, Denys Vlasenko wrote: >>> On 07/05/2013 01:18 PM, Florian Kelbert wrote: >>>> Hi all, >>>> >>>> while trying to strace nginx (http://nginx.org/), using strace -f, I >>>> realized that strace fails to trace a forked child process. >>> >>> Which version of strace and kernel do you have? >> >> I compiled strace 4.8 from the sources using ./configure && make; using >> Ubuntu 13.04, kernel 3.8.0-25 >> >>> >>> Can you show the same event with -d option added to strace >>> command line? (the debug output goes to stderr, not -o LOGFILE). >>> >> >> ./strace -f -d ~/nginx/sbin/nginx >> >> http://pastebin.com/ZwHXHrWa >> >> Process 7428 is born in line 518 and survives the subsequent exit_group() by >> process 7427, as the output of ps shows: > > The log shows that exit_group(0) is indeed called immediately after clone(), > making "strace exited too early to see the child" theory feasible. > > Can you test this theory by replacing > > while (nprocs != 0) > > with > > while (1) > > in strace.c in function trace()? > > The exit from trace loop will then happen when we receive ECHILD. > In my testing it worked. >
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