diff options
| author | Michel Lespinasse <walken@google.com> | 2011-03-10 18:48:51 -0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-03-11 12:23:08 +0100 |
| commit | 37a9d912b24f96a0591773e6e6c3642991ae5a70 (patch) | |
| tree | 5c4d5b9a52e2c533269e589115afbd25b6c8534b /arch/alpha | |
| parent | 522d7decc0370070448a8c28982c8dfd8970489e (diff) | |
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/alpha')
| -rw-r--r-- | arch/alpha/include/asm/futex.h | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/arch/alpha/include/asm/futex.h b/arch/alpha/include/asm/futex.h index 945de222ab9..c4e5c2850cc 100644 --- a/arch/alpha/include/asm/futex.h +++ b/arch/alpha/include/asm/futex.h @@ -81,21 +81,22 @@ static inline int 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) { - int prev, cmp; + int ret = 0, prev, cmp; if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; __asm__ __volatile__ ( __ASM_SMP_MB - "1: ldl_l %0,0(%2)\n" - " cmpeq %0,%3,%1\n" - " beq %1,3f\n" - " mov %4,%1\n" - "2: stl_c %1,0(%2)\n" - " beq %1,4f\n" + "1: ldl_l %1,0(%3)\n" + " cmpeq %1,%4,%2\n" + " beq %2,3f\n" + " mov %5,%2\n" + "2: stl_c %2,0(%3)\n" + " beq %2,4f\n" "3: .subsection 2\n" "4: br 1b\n" " .previous\n" @@ -105,11 +106,12 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) " .long 2b-.\n" " lda $31,3b-2b(%0)\n" " .previous\n" - : "=&r"(prev), "=&r"(cmp) + : "+r"(ret), "=&r"(prev), "=&r"(cmp) : "r"(uaddr), "r"((long)oldval), "r"(newval) : "memory"); - return prev; + *uval = prev; + return ret; } #endif /* __KERNEL__ */ |