[Bug 713237] [NEW] shutdown segv due to race w/ free_waiter threads

[dann frazier]

Public bug reported:

Binary package hint: multipath-tools

I received a coredump from a customer (running a lucid-based system).
Analyzing the core from multipathd shows that we are crashing in waiter.c::free_waiter().

void free_waiter (void *data)
{
 struct event_thread *wp = (struct event_thread *)data;

 /*
  * indicate in mpp that the wp is already freed storage
  */
 lock(wp->vecs->lock);

 if (wp->mpp)
  /*
   * be careful, mpp may already be freed -- null if so
   */
  wp->mpp->waiter = NULL;
 else
  condlog(3, "free_waiter, mpp freed before wp=%p,", wp);

 unlock(wp->vecs->lock); <<< Crashing here

 if (wp->dmt)
  dm_task_destroy(wp->dmt);

 FREE(wp);
}

The lock is NULL:

(gdb) print wp->vecs->lock
$3 = (pthread_mutex_t *) 0x0

This appears to be the upstream issue fixed here:
http://git.kernel.org/gitweb.cgi?p=linux/storage/multipath-tools/.git;a=commitdiff;h=a403f57b991f3be7c7ea6250d95fad1554c9d6ca

This fix is currently missing from all versions of multipath-tools in
lucid->natty.

(The original customer issue was filed in the private bug #712875.)

** Affects: multipath-tools (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/713237

Title:
  shutdown segv due to race w/ free_waiter threads