On Mon, 12 May 2014, Darren Hart wrote:
> On Mon, May 12, 2014 at 08:45:32PM -0000, Thomas Gleixner wrote:
> > strace tells me:
> >
> > futex(0x600e00, FUTEX_LOCK_PI_PRIVATE, 1) = -1 EINVAL (Invalid argument)
> >
> > but the return value of pthread_mutex_lock() is 0
>
> So something is clearly wrong there - however, were you looking at the
> comments
> (sorry, I mean the C code), or the implementation (all the ASM)? The only way
> I've been able to be sure in the past is to delete the ASM files and recompile
> using the C files. Hopefully we'll be able to drop all the ASM in the pthread
> calls soonish (measured in years in glibc development time scales).... sigh.
The C implementation does:
if (INTERNAL_SYSCALL_ERROR_P (e, __err)
&& (INTERNAL_SYSCALL_ERRNO (e, __err) == ESRCH
|| INTERNAL_SYSCALL_ERRNO (e, __err) == EDEADLK))
{
assert (INTERNAL_SYSCALL_ERRNO (e, __err) != EDEADLK
|| (kind != PTHREAD_MUTEX_ERRORCHECK_NP
&& kind != PTHREAD_MUTEX_RECURSIVE_NP));
/* ESRCH can happen only for non-robust PI mutexes where
the owner of the lock died. */
assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust);
/* Delay the thread indefinitely. */
while (1)
pause_not_cancel ();
}
So anything else than ESRCH and EDEADLK is ignored and then the thing
happily returns 0 at the end. Unlock is the same:
{
int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
int private = (robust
? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
: PTHREAD_MUTEX_PSHARED (mutex));
INTERNAL_SYSCALL_DECL (__err);
INTERNAL_SYSCALL (futex, __err, 2, &mutex->__data.__lock,
__lll_private_flag (FUTEX_UNLOCK_PI, private));
}
Quality stuff that.
Thanks,
tglx
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