[2/2] pthread_once: Use futex wrappers with error checking.
Commit Message
On Thu, 2014-12-04 at 16:36 -0800, Roland McGrath wrote:
> > - /* Same generation, some other thread was faster. Wait. */
> > - lll_futex_wait (once_control, newval, LLL_PRIVATE);
> > + /* Same generation, some other thread was faster. Wait and
> > + retry. Ignore the return value because all possible
> > + values (0, -EWOULDBLOCK, -EINTR) need to be handled the
> > + same. */
>
> Two spaces between sentences, even when it was wrong before.
> Always mention EAGAIN rather than EWOULDBLOCK.
>
> Use ignore_value rather than only a comment, to be more explicit about a
> correct case of ignoring errors. Then we can use warn_unused_result on all
> the new inlines, and turn up cases where failing to check for errors is
> dubious (we have many today).
>
> Aside from those nits, this change is fine and good once we've settled on
> the new internal API details.
Updated patch attached. If there's no objection, and once we have
agreed on a Patch 1/2 that can be committed, I will commit this one as
well.
Comments
> - lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
> + futex_wake ((unsigned int *)once_control, INT_MAX, FUTEX_PRIVATE);
Always put a space after a cast.
> + ignore_value (futex_wait ((unsigned int *)once_control,
> + (unsigned)newval, FUTEX_PRIVATE));
Ditto, and always 'unsigned int', never 'unsigned'.
> - lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
> + futex_wake ((unsigned int *)once_control, INT_MAX, FUTEX_PRIVATE);
Space here too.
commit 5858b0ec69ff188310c049ec27b102303c38b7b3
Author: Torvald Riegel <triegel@redhat.com>
Date: Thu Dec 4 14:29:27 2014 +0100
pthread_once: Use futex wrappers with error checking.
@@ -17,8 +17,9 @@
<http://www.gnu.org/licenses/>. */
#include "pthreadP.h"
-#include <lowlevellock.h>
+#include <futex-internal.h>
#include <atomic.h>
+#include <libc-internal.h>
unsigned long int __fork_generation attribute_hidden;
@@ -35,7 +36,7 @@ clear_once_control (void *arg)
get interrupted (see __pthread_once), so all we need to relay to other
threads is the state being reset again. */
atomic_store_relaxed (once_control, 0);
- lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
+ futex_wake ((unsigned int *)once_control, INT_MAX, FUTEX_PRIVATE);
}
@@ -100,8 +101,11 @@ __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void))
is set and __PTHREAD_ONCE_DONE is not. */
if (val == newval)
{
- /* Same generation, some other thread was faster. Wait. */
- lll_futex_wait (once_control, newval, LLL_PRIVATE);
+ /* Same generation, some other thread was faster. Wait and
+ retry. Ignore the return value because all possible
+ values (0, EAGAIN, EINTR) need to be handled the same. */
+ ignore_value (futex_wait ((unsigned int *)once_control,
+ (unsigned)newval, FUTEX_PRIVATE));
continue;
}
}
@@ -122,7 +126,7 @@ __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void))
atomic_store_release (once_control, __PTHREAD_ONCE_DONE);
/* Wake up all other threads. */
- lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
+ futex_wake ((unsigned int *)once_control, INT_MAX, FUTEX_PRIVATE);
break;
}