futex: remove FUTEX_REQUEUE_PI (non CMP)
The new requeue PI futex op codes were modeled after the existing
FUTEX_REQUEUE and FUTEX_CMP_REQUEUE calls. I was unaware at the time
that FUTEX_REQUEUE was only around for compatibility reasons and
shouldn't be used in new code. Ulrich Drepper elaborates on this in his
Futexes are Tricky paper: http://people.redhat.com/drepper/futex.pdf.
The deprecated call doesn't catch changes to the futex corresponding to
the destination futex which can lead to deadlock.
Therefor, I feel it best to remove FUTEX_REQUEUE_PI and leave only
FUTEX_CMP_REQUEUE_PI as there are not yet any existing users of the API.
This patch does change the OP code value of FUTEX_CMP_REQUEUE_PI to 12
from 13. Since my test case is the only known user of this API, I felt
this was the right thing to do, rather than leave a hole in the
enumeration.
I chose to continue using the _CMP_ modifier in the OP code to make it
explicit to the user that the test is being done.
Builds, boots, and ran several hundred iterations requeue_pi.c.
Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
LKML-Reference: <49ED580E.1050502@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/futex.c b/kernel/futex.c
index 6d2daa4..aec8bf8 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2555,9 +2555,6 @@
ret = futex_wait_requeue_pi(uaddr, fshared, val, timeout, val3,
clockrt, uaddr2);
break;
- case FUTEX_REQUEUE_PI:
- ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL, 1);
- break;
case FUTEX_CMP_REQUEUE_PI:
ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
1);
@@ -2596,8 +2593,7 @@
* number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
*/
if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
- cmd == FUTEX_REQUEUE_PI || cmd == FUTEX_CMP_REQUEUE_PI ||
- cmd == FUTEX_WAKE_OP)
+ cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
val2 = (u32) (unsigned long) utime;
return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);