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From: "john.ogness at linutronix dot de" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nptl/11588] pthread condvars are not priority inheritance aware
Date: Thu, 20 Feb 2014 17:44:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=11588

John Ogness <john.ogness at linutronix dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |john.ogness at linutronix dot de

--- Comment #32 from John Ogness <john.ogness at linutronix dot de> ---
I believe there is an error in [PATCH 1/3 V3] where COND_PRIO_PROTECT will
clobber the CLOCKID in cond->__data.__nwaiters. This is because the
COND_PROTOCOL values are not shifted by COND_PROTOCOL_SHIFT before reading and
writing to __nwaiters.

I believe the switch cases in pthread_cond_init.c:__pthread_cond_init() should
look like this:

    case PTHREAD_PRIO_INHERIT:
      cond->__data.__nwaiters |= COND_PRIO_INHERIT << COND_PROTOCOL_SHIFT;
      break;

    case PTHREAD_PRIO_PROTECT:
      cond->__data.__nwaiters |= COND_PRIO_PROTECT << COND_PROTOCOL_SHIFT;
      break;


And the cond_lock() and cond_unlock() in cond-lock.h should look like this:

static inline void
cond_lock(pthread_cond_t *cond, int pshared)
{
  if (pshared == LLL_PRIVATE
      && (((cond->__data.__nwaiters & COND_PROTOCOL_MASK) >>
COND_PROTOCOL_SHIFT)
         == COND_PRIO_INHERIT))
    lll_pi_lock (cond->__data.__lock, pshared);
  else
    lll_lock (cond->__data.__lock, pshared);
}

static inline void
cond_unlock(pthread_cond_t *cond, int pshared)
{
  if (pshared == LLL_PRIVATE
      && (((cond->__data.__nwaiters & COND_PROTOCOL_MASK) >>
COND_PROTOCOL_SHIFT)
         == COND_PRIO_INHERIT))
    lll_pi_unlock (cond->__data.__lock, pshared);
  else
    lll_unlock (cond->__data.__lock, pshared);
}

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