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From: "msebor at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nptl/18435] New: pthread_once hangs when init routine throws an exception
Date: Wed, 20 May 2015 00:06:00 -0000
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X-Bugzilla-Product: glibc
X-Bugzilla-Component: nptl
X-Bugzilla-Version: 2.21
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X-Bugzilla-Who: msebor at redhat dot com
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https://sourceware.org/bugzilla/show_bug.cgi?id=18435

            Bug ID: 18435
           Summary: pthread_once hangs when init routine throws an
                    exception
           Product: glibc
           Version: 2.21
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: msebor at redhat dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

As discussed in http://gcc.gnu.org/bugzilla/show_bug.cgi?id=66146, pthread_once
on at least ARM and PowerPC (but not x86_64) doesn't interact well with C++
exceptions thrown from the init routine.  The following test case demonstrates
the problem: it hangs in pthread_once until it's interrupted by SIGALRM.  The
test case runs successfully to completion on x86_64.

$ cat /home/remote/msebor/tmp/once.cc && g++ -Wall -g -lpthread
/home/remote/msebor/tmp/once.cc && gdb -batch -q -ex "catch signal SIGALRM" -ex
r -ex bt ./a.out
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

static pthread_once_t once = PTHREAD_ONCE_INIT;
struct OnceException { };

static int niter;

static void init_routine (void) {
  if (niter < 2)
    throw OnceException ();
}

int main (void) {
  int result = 1;

  alarm (5);

  for (niter = 0; niter != 3; ++niter) {

    try {
      int rc = pthread_once (&once, init_routine);
      if (rc)
        fprintf (stderr, "pthread_once failed: %i (%s)\n",
                 rc, strerror (rc));

      if (niter < 2)
        fputs ("pthread_once unexpectedly returned without"
               " throwing an exception", stderr);
    }
    catch (OnceException) {
      if (1 < niter)
        fputs ("pthread_once unexpectedly threw", stderr);
      result = 0;
    }
    catch (...) {
      fputs ("pthread_once threw an unknown exception", stderr);
    }

    if (result)
      break;
  }

  return result;
}
Catchpoint 1 (signal SIGALRM)
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/power8/libthread_db.so.1".

Catchpoint 1 (signal SIGALRM), 0x00003fffb7f4f7bc in pthread_once () from
/lib64/power8/libpthread.so.0
#0  0x00003fffb7f4f7bc in pthread_once () from /lib64/power8/libpthread.so.0
#1  0x0000000010000c0c in main () at /home/remote/msebor/tmp/once.cc:25

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