diff options
| author | Darren Hart <dvhltc@us.ibm.com> | 2009-04-20 22:22:22 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-04-30 11:41:35 +0200 |
| commit | ba9c22f2c01cf5c88beed5a6b9e07d42e10bd358 (patch) | |
| tree | 77664171b51bb6b03eac13ee946b6d894b2da01d /kernel/futex.c | |
| parent | a5a2a0c7fa039c59619bc908b3b1ed24734d442a (diff) | |
| download | lwn-ba9c22f2c01cf5c88beed5a6b9e07d42e10bd358.tar.gz lwn-ba9c22f2c01cf5c88beed5a6b9e07d42e10bd358.zip | |
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>
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 6 |
1 files changed, 1 insertions, 5 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 6d2daa46f9ff..aec8bf89bf4e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2555,9 +2555,6 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, 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 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, * 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); |