[Bug nptl/33717] New: nptl: pthread_join/pthread_timedjoin_np/pthread_clockjoin_np might not act as cancellation entrypoint

[adhemerval.zanella at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=33717

            Bug ID: 33717
           Summary: nptl:
                    pthread_join/pthread_timedjoin_np/pthread_clockjoin_np
                    might not act as cancellation entrypoint
           Product: glibc
           Version: 2.13
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: adhemerval.zanella at linaro dot org
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

The pthread_join/pthread_timedjoin_np/pthread_clockjoin_np will not act
on cancellation if 1. some other thread is already waiting on the 'joinid' or
2. if the thread has already exited.

On nptl/pthread_join_common.c, the 1. is due the CAS doing an early return:

 80   else if (__glibc_unlikely (atomic_compare_exchange_weak_acquire
(&pd->joinid,
 81                                                                    &self,
 82                                                                    NULL)))
 83     /* There is already somebody waiting for the thread.  */
 84     return EINVAL;

And 2. is due the pd->tid equal to 0:

 99       pid_t tid;
100       while ((tid = atomic_load_acquire (&pd->tid)) != 0)
101         {

The easiest solution would to add an __pthread_testcancel () on
__pthread_clockjoin_ex () if 'cancel' is true.

-- 
You are receiving this mail because:
You are on the CC list for the bug.