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2.1preview1 #2

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schmurfy opened this issue Nov 13, 2013 · 2 comments
Closed

2.1preview1 #2

schmurfy opened this issue Nov 13, 2013 · 2 comments

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@schmurfy
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is the preview1 release supported or does it requires a more recent one ?

I just tried it but I get some "Symbol not found: _rb_profile_frames" errors :(
@tmm1
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tmm1 commented Nov 13, 2013

This function was recently added to trunk. You'll need to roll your own build.

@schmurfy
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ok thanks.

XrXr added a commit to XrXr/stackprof that referenced this issue Dec 10, 2024
@XrXr
Fix race with timer signal in stackprof_start()
bd7516d 
I got a SEGV core dump with the stack trace as follows:

    #0  __pthread_kill_implementation (no_tid=0, signo=14, threadid=0) at ./nptl/pthread_kill.c:50
    tmm1#1  __pthread_kill_internal (signo=14, threadid=0) at ./nptl/pthread_kill.c:78
    tmm1#2  __GI___pthread_kill (threadid=0, signo=14) at ./nptl/pthread_kill.c:89
    tmm1#3  <signal handler called> () at /lib/x86_64-linux-gnu/libc.so.6
    tmm1#4  stackprof_start (argc=<optimized out>, argv=<optimized out>, self=<optimized out>) at stackprof.c:228
    tmm1#5  vm_call_cfunc_with_frame_
    ...

Notice that `threadid=0` in the top frame -- the SEGV comes from inside
libc as it tries to dereference `threadid`.

The signal comes from stackprof's signal handler:

    if (pthread_self() != _stackprof.target_thread) {
        pthread_kill(_stackprof.target_thread, sig);
        return;
    }

During stackprof_start(), `_stackprof.target_thread` is 0.

You can recreate the stack trace in the crash with a program that does
`pthread_kill(0, SIGALRM)`:

    #include <signal.h>

    int
    main(void)
    {
       pthread_kill(0, SIGALRM);
    }

Only set `running` after target_thread is set to avoid this crash in
case the timer expires after `settimer()` but before setting
`target_thread`.

Also, since the ordering is important here, make `running`
`volatile sig_atomic_t` to prevent the compiler from doing unwanted
reordering.
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@tmm1 @schmurfy