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| author | Michel Lespinasse <walken@google.com> | 2011-03-11 02:48:51 (GMT) |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-03-11 11:23:08 (GMT) |
| commit | 37a9d912b24f96a0591773e6e6c3642991ae5a70 (patch) | |
| tree | 5c4d5b9a52e2c533269e589115afbd25b6c8534b /arch/ia64/include | |
| parent | 522d7decc0370070448a8c28982c8dfd8970489e (diff) | |
| download | linux-37a9d912b24f96a0591773e6e6c3642991ae5a70.tar.xz | |
futex: Sanitize cmpxchg_futex_value_locked API
The cmpxchg_futex_value_locked API was funny in that it returned either
the original, user-exposed futex value OR an error code such as -EFAULT.
This was confusing at best, and could be a source of livelocks in places
that retry the cmpxchg_futex_value_locked after trying to fix the issue
by running fault_in_user_writeable().
This change makes the cmpxchg_futex_value_locked API more similar to the
get_futex_value_locked one, returning an error code and updating the
original value through a reference argument.
Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Chris Metcalf <cmetcalf@tilera.com> [tile]
Acked-by: Tony Luck <tony.luck@intel.com> [ia64]
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michal Simek <monstr@monstr.eu> [microblaze]
Acked-by: David Howells <dhowells@redhat.com> [frv]
Cc: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20110311024851.GC26122@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/ia64/include')
| -rw-r--r-- | arch/ia64/include/asm/futex.h | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/ia64/include/asm/futex.h b/arch/ia64/include/asm/futex.h index c7f0f06..b072840 100644 --- a/arch/ia64/include/asm/futex.h +++ b/arch/ia64/include/asm/futex.h @@ -100,23 +100,26 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr) } static inline int -futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) +futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr, + int oldval, int newval) { if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; { - register unsigned long r8 __asm ("r8"); + register unsigned long r8 __asm ("r8") = 0; + unsigned long prev; __asm__ __volatile__( " mf;; \n" " mov ar.ccv=%3;; \n" "[1:] cmpxchg4.acq %0=[%1],%2,ar.ccv \n" " .xdata4 \"__ex_table\", 1b-., 2f-. \n" "[2:]" - : "=r" (r8) + : "=r" (prev) : "r" (uaddr), "r" (newval), "rO" ((long) (unsigned) oldval) : "memory"); + *uval = prev; return r8; } } |