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 /include/linux/futex.h | |
| parent | futex: fix futex_wait_setup key handling (diff) | |
| download | wireguard-linux-ba9c22f2c01cf5c88beed5a6b9e07d42e10bd358.tar.xz wireguard-linux-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 'include/linux/futex.h')
| -rw-r--r-- | include/linux/futex.h | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/include/linux/futex.h b/include/linux/futex.h index b05519ca9e57..34956c8fdebf 100644 --- a/include/linux/futex.h +++ b/include/linux/futex.h @@ -24,8 +24,7 @@ union ktime; #define FUTEX_WAIT_BITSET 9 #define FUTEX_WAKE_BITSET 10 #define FUTEX_WAIT_REQUEUE_PI 11 -#define FUTEX_REQUEUE_PI 12 -#define FUTEX_CMP_REQUEUE_PI 13 +#define FUTEX_CMP_REQUEUE_PI 12 #define FUTEX_PRIVATE_FLAG 128 #define FUTEX_CLOCK_REALTIME 256 @@ -43,7 +42,6 @@ union ktime; #define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITS | FUTEX_PRIVATE_FLAG) #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG) -#define FUTEX_REQUEUE_PI_PRIVATE (FUTEX_REQUEUE_PI | FUTEX_PRIVATE_FLAG) #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG) |