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Subject[PATCH] futex: cmpxchg_futex_value_locked API change
Aplogies for the long CC list - as this proposal involves asm changes
in many architectures, and I have only been able to test on x86,
I have tried to include one maintainer from every arch so they can
hopefully double check me. I do think I got all architectures right,
but you can never be 100% sure...

------------------------------------8<---------------------------------
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>
---
arch/alpha/include/asm/futex.h | 22 +++++++++-------
arch/arm/include/asm/futex.h | 23 +++++++++--------
arch/frv/include/asm/futex.h | 3 +-
arch/ia64/include/asm/futex.h | 9 ++++--
arch/microblaze/include/asm/futex.h | 24 ++++++++++--------
arch/mips/include/asm/futex.h | 32 +++++++++++++-----------
arch/parisc/include/asm/futex.h | 18 +++++++-------
arch/powerpc/include/asm/futex.h | 20 ++++++++-------
arch/s390/include/asm/futex.h | 4 +-
arch/s390/include/asm/uaccess.h | 2 +-
arch/s390/lib/uaccess.h | 4 +-
arch/s390/lib/uaccess_pt.c | 13 ++++++----
arch/s390/lib/uaccess_std.c | 6 +++-
arch/sh/include/asm/futex-irq.h | 9 +++----
arch/sh/include/asm/futex.h | 5 ++-
arch/sparc/include/asm/futex_64.h | 16 +++++++----
arch/tile/include/asm/futex.h | 7 +++--
arch/x86/include/asm/futex.h | 16 +++++++-----
include/asm-generic/futex.h | 3 +-
kernel/futex.c | 46 ++++++++++++----------------------
20 files changed, 147 insertions(+), 135 deletions(-)
diff --git a/arch/alpha/include/asm/futex.h b/arch/alpha/include/asm/futex.h
index 945de22..c4e5c28 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__ */
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index b33fe70..d20b78f 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -88,36 +88,37 @@ 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 val;
+ int ret = 0, val;

if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

- pagefault_disable(); /* implies preempt_disable() */
+ /* Note that preemption is disabled by futex_atomic_cmpxchg_inatomic
+ * call sites. */

__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
- "1: " T(ldr) " %0, [%3]\n"
- " teq %0, %1\n"
+ "1: " T(ldr) " %1, [%4]\n"
+ " teq %1, %2\n"
" it eq @ explicit IT needed for the 2b label\n"
- "2: " T(streq) " %2, [%3]\n"
+ "2: " T(streq) " %3, [%4]\n"
"3:\n"
" .pushsection __ex_table,\"a\"\n"
" .align 3\n"
" .long 1b, 4f, 2b, 4f\n"
" .popsection\n"
" .pushsection .fixup,\"ax\"\n"
- "4: mov %0, %4\n"
+ "4: mov %0, %5\n"
" b 3b\n"
" .popsection"
- : "=&r" (val)
+ : "+r" (ret), "=&r" (val)
: "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
: "cc", "memory");

- pagefault_enable(); /* subsumes preempt_enable() */
-
- return val;
+ *uval = val;
+ return ret;
}

#endif /* !SMP */
diff --git a/arch/frv/include/asm/futex.h b/arch/frv/include/asm/futex.h
index 08b3d1d..0548f8e 100644
--- a/arch/frv/include/asm/futex.h
+++ b/arch/frv/include/asm/futex.h
@@ -10,7 +10,8 @@
extern 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)
{
return -ENOSYS;
}
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;
}
}
diff --git a/arch/microblaze/include/asm/futex.h b/arch/microblaze/include/asm/futex.h
index ad3fd61..fa019ed 100644
--- a/arch/microblaze/include/asm/futex.h
+++ b/arch/microblaze/include/asm/futex.h
@@ -94,31 +94,33 @@ 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__ ("1: lwx %0, %2, r0; \
- cmp %1, %0, %3; \
- beqi %1, 3f; \
- 2: swx %4, %2, r0; \
- addic %1, r0, 0; \
- bnei %1, 1b; \
+ __asm__ __volatile__ ("1: lwx %1, %3, r0; \
+ cmp %2, %1, %4; \
+ beqi %2, 3f; \
+ 2: swx %5, %3, r0; \
+ addic %2, r0, 0; \
+ bnei %2, 1b; \
3: \
.section .fixup,\"ax\"; \
4: brid 3b; \
- addik %0, r0, %5; \
+ addik %0, r0, %6; \
.previous; \
.section __ex_table,\"a\"; \
.word 1b,4b,2b,4b; \
.previous;" \
- : "=&r" (prev), "=&r"(cmp) \
+ : "+r" (ret), "=&r" (prev), "=&r"(cmp) \
: "r" (uaddr), "r" (oldval), "r" (newval), "i" (-EFAULT));

- return prev;
+ *uval = prev;
+ return ret;
}

#endif /* __KERNEL__ */
diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h
index b9cce90..692a24b 100644
--- a/arch/mips/include/asm/futex.h
+++ b/arch/mips/include/asm/futex.h
@@ -132,9 +132,10 @@ 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 retval;
+ int ret = 0, val;

if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;
@@ -145,25 +146,25 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
" .set push \n"
" .set noat \n"
" .set mips3 \n"
- "1: ll %0, %2 \n"
- " bne %0, %z3, 3f \n"
+ "1: ll %1, %3 \n"
+ " bne %1, %z4, 3f \n"
" .set mips0 \n"
- " move $1, %z4 \n"
+ " move $1, %z5 \n"
" .set mips3 \n"
- "2: sc $1, %1 \n"
+ "2: sc $1, %2 \n"
" beqzl $1, 1b \n"
__WEAK_LLSC_MB
"3: \n"
" .set pop \n"
" .section .fixup,\"ax\" \n"
- "4: li %0, %5 \n"
+ "4: li %0, %6 \n"
" j 3b \n"
" .previous \n"
" .section __ex_table,\"a\" \n"
" "__UA_ADDR "\t1b, 4b \n"
" "__UA_ADDR "\t2b, 4b \n"
" .previous \n"
- : "=&r" (retval), "=R" (*uaddr)
+ : "+r" (ret), "=&r" (val), "=R" (*uaddr)
: "R" (*uaddr), "Jr" (oldval), "Jr" (newval), "i" (-EFAULT)
: "memory");
} else if (cpu_has_llsc) {
@@ -172,31 +173,32 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
" .set push \n"
" .set noat \n"
" .set mips3 \n"
- "1: ll %0, %2 \n"
- " bne %0, %z3, 3f \n"
+ "1: ll %1, %3 \n"
+ " bne %1, %z4, 3f \n"
" .set mips0 \n"
- " move $1, %z4 \n"
+ " move $1, %z5 \n"
" .set mips3 \n"
- "2: sc $1, %1 \n"
+ "2: sc $1, %2 \n"
" beqz $1, 1b \n"
__WEAK_LLSC_MB
"3: \n"
" .set pop \n"
" .section .fixup,\"ax\" \n"
- "4: li %0, %5 \n"
+ "4: li %0, %6 \n"
" j 3b \n"
" .previous \n"
" .section __ex_table,\"a\" \n"
" "__UA_ADDR "\t1b, 4b \n"
" "__UA_ADDR "\t2b, 4b \n"
" .previous \n"
- : "=&r" (retval), "=R" (*uaddr)
+ : "+r" (ret), "=&r" (val), "=R" (*uaddr)
: "R" (*uaddr), "Jr" (oldval), "Jr" (newval), "i" (-EFAULT)
: "memory");
} else
return -ENOSYS;

- return retval;
+ *uval = val;
+ return ret;
}

#endif
diff --git a/arch/parisc/include/asm/futex.h b/arch/parisc/include/asm/futex.h
index 0c705c3..4c6d867 100644
--- a/arch/parisc/include/asm/futex.h
+++ b/arch/parisc/include/asm/futex.h
@@ -51,10 +51,10 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)

/* Non-atomic version */
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 err = 0;
- int uval;
+ int val;

/* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is
* our gateway page, and causes no end of trouble...
@@ -65,12 +65,12 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

- err = get_user(uval, uaddr);
- if (err) return -EFAULT;
- if (uval == oldval)
- err = put_user(newval, uaddr);
- if (err) return -EFAULT;
- return uval;
+ if (get_user(val, uaddr))
+ return -EFAULT;
+ if (val == oldval && put_user(newval, uaddr))
+ return -EFAULT;
+ *uval = val;
+ return 0;
}

#endif /*__KERNEL__*/
diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h
index 7c589ef..631e8da 100644
--- a/arch/powerpc/include/asm/futex.h
+++ b/arch/powerpc/include/asm/futex.h
@@ -82,35 +82,37 @@ 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;
+ int ret = 0, prev;

if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

__asm__ __volatile__ (
PPC_RELEASE_BARRIER
-"1: lwarx %0,0,%2 # futex_atomic_cmpxchg_inatomic\n\
- cmpw 0,%0,%3\n\
+"1: lwarx %1,0,%3 # futex_atomic_cmpxchg_inatomic\n\
+ cmpw 0,%1,%4\n\
bne- 3f\n"
- PPC405_ERR77(0,%2)
-"2: stwcx. %4,0,%2\n\
+ PPC405_ERR77(0,%3)
+"2: stwcx. %5,0,%3\n\
bne- 1b\n"
PPC_ACQUIRE_BARRIER
"3: .section .fixup,\"ax\"\n\
-4: li %0,%5\n\
+4: li %0,%6\n\
b 3b\n\
.previous\n\
.section __ex_table,\"a\"\n\
.align 3\n\
" PPC_LONG "1b,4b,2b,4b\n\
.previous" \
- : "=&r" (prev), "+m" (*uaddr)
+ : "+r" (ret), "=&r" (prev), "+m" (*uaddr)
: "r" (uaddr), "r" (oldval), "r" (newval), "i" (-EFAULT)
: "cc", "memory");

- return prev;
+ *uval = prev;
+ return ret;
}

#endif /* __KERNEL__ */
diff --git a/arch/s390/include/asm/futex.h b/arch/s390/include/asm/futex.h
index 5c5d02d..27ac515 100644
--- a/arch/s390/include/asm/futex.h
+++ b/arch/s390/include/asm/futex.h
@@ -39,13 +39,13 @@ static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
return ret;
}

-static inline int futex_atomic_cmpxchg_inatomic(int __user *uaddr,
+static inline int futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr,
int oldval, int newval)
{
if (! access_ok (VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

- return uaccess.futex_atomic_cmpxchg(uaddr, oldval, newval);
+ return uaccess.futex_atomic_cmpxchg(uval, uaddr, oldval, newval);
}

#endif /* __KERNEL__ */
diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index d6b1ed0..549adf6 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -84,7 +84,7 @@ struct uaccess_ops {
size_t (*strnlen_user)(size_t, const char __user *);
size_t (*strncpy_from_user)(size_t, const char __user *, char *);
int (*futex_atomic_op)(int op, int __user *, int oparg, int *old);
- int (*futex_atomic_cmpxchg)(int __user *, int old, int new);
+ int (*futex_atomic_cmpxchg)(int *, int __user *, int old, int new);
};

extern struct uaccess_ops uaccess;
diff --git a/arch/s390/lib/uaccess.h b/arch/s390/lib/uaccess.h
index 126011d..89a8067 100644
--- a/arch/s390/lib/uaccess.h
+++ b/arch/s390/lib/uaccess.h
@@ -12,12 +12,12 @@ extern size_t copy_from_user_std(size_t, const void __user *, void *);
extern size_t copy_to_user_std(size_t, void __user *, const void *);
extern size_t strnlen_user_std(size_t, const char __user *);
extern size_t strncpy_from_user_std(size_t, const char __user *, char *);
-extern int futex_atomic_cmpxchg_std(int __user *, int, int);
+extern int futex_atomic_cmpxchg_std(int *, int __user *, int, int);
extern int futex_atomic_op_std(int, int __user *, int, int *);

extern size_t copy_from_user_pt(size_t, const void __user *, void *);
extern size_t copy_to_user_pt(size_t, void __user *, const void *);
extern int futex_atomic_op_pt(int, int __user *, int, int *);
-extern int futex_atomic_cmpxchg_pt(int __user *, int, int);
+extern int futex_atomic_cmpxchg_pt(int *, int __user *, int, int);

#endif /* __ARCH_S390_LIB_UACCESS_H */
diff --git a/arch/s390/lib/uaccess_pt.c b/arch/s390/lib/uaccess_pt.c
index 404f2de..e4f9ad8 100644
--- a/arch/s390/lib/uaccess_pt.c
+++ b/arch/s390/lib/uaccess_pt.c
@@ -354,26 +354,29 @@ int futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old)
return ret;
}

-static int __futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
+static int __futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr,
+ int oldval, int newval)
{
int ret;

asm volatile("0: cs %1,%4,0(%5)\n"
- "1: lr %0,%1\n"
+ "1: l %0,0\n"
"2:\n"
EX_TABLE(0b,2b) EX_TABLE(1b,2b)
: "=d" (ret), "+d" (oldval), "=m" (*uaddr)
: "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
: "cc", "memory" );
+ *uval = oldval;
return ret;
}

-int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
+int futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr,
+ int oldval, int newval)
{
int ret;

if (segment_eq(get_fs(), KERNEL_DS))
- return __futex_atomic_cmpxchg_pt(uaddr, oldval, newval);
+ return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
spin_lock(&current->mm->page_table_lock);
uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
if (!uaddr) {
@@ -382,7 +385,7 @@ int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
}
get_page(virt_to_page(uaddr));
spin_unlock(&current->mm->page_table_lock);
- ret = __futex_atomic_cmpxchg_pt(uaddr, oldval, newval);
+ ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
put_page(virt_to_page(uaddr));
return ret;
}
diff --git a/arch/s390/lib/uaccess_std.c b/arch/s390/lib/uaccess_std.c
index a6c4f7e..5c568b3 100644
--- a/arch/s390/lib/uaccess_std.c
+++ b/arch/s390/lib/uaccess_std.c
@@ -287,19 +287,21 @@ int futex_atomic_op_std(int op, int __user *uaddr, int oparg, int *old)
return ret;
}

-int futex_atomic_cmpxchg_std(int __user *uaddr, int oldval, int newval)
+int futex_atomic_cmpxchg_std(int *uval, int __user *uaddr,
+ int oldval, int newval)
{
int ret;

asm volatile(
" sacf 256\n"
"0: cs %1,%4,0(%5)\n"
- "1: lr %0,%1\n"
+ "1: l %0,0\n"
"2: sacf 0\n"
EX_TABLE(0b,2b) EX_TABLE(1b,2b)
: "=d" (ret), "+d" (oldval), "=m" (*uaddr)
: "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
: "cc", "memory" );
+ *uval = oldval;
return ret;
}

diff --git a/arch/sh/include/asm/futex-irq.h b/arch/sh/include/asm/futex-irq.h
index a9f16a7..7b701cb 100644
--- a/arch/sh/include/asm/futex-irq.h
+++ b/arch/sh/include/asm/futex-irq.h
@@ -88,7 +88,8 @@ static inline int atomic_futex_op_xchg_xor(int oparg, int __user *uaddr,
return ret;
}

-static inline int atomic_futex_op_cmpxchg_inatomic(int __user *uaddr,
+static inline int atomic_futex_op_cmpxchg_inatomic(int *uval,
+ int __user *uaddr,
int oldval, int newval)
{
unsigned long flags;
@@ -102,10 +103,8 @@ static inline int atomic_futex_op_cmpxchg_inatomic(int __user *uaddr,

local_irq_restore(flags);

- if (ret)
- return ret;
-
- return prev;
+ *uval = prev;
+ return ret;
}

#endif /* __ASM_SH_FUTEX_IRQ_H */
diff --git a/arch/sh/include/asm/futex.h b/arch/sh/include/asm/futex.h
index 68256ec..a8a5125 100644
--- a/arch/sh/include/asm/futex.h
+++ b/arch/sh/include/asm/futex.h
@@ -65,12 +65,13 @@ 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)
{
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

- return atomic_futex_op_cmpxchg_inatomic(uaddr, oldval, newval);
+ return atomic_futex_op_cmpxchg_inatomic(uval, uaddr, oldval, newval);
}

#endif /* __KERNEL__ */
diff --git a/arch/sparc/include/asm/futex_64.h b/arch/sparc/include/asm/futex_64.h
index 47f9583..e086220 100644
--- a/arch/sparc/include/asm/futex_64.h
+++ b/arch/sparc/include/asm/futex_64.h
@@ -85,26 +85,30 @@ 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 ret = 0;
+
__asm__ __volatile__(
- "\n1: casa [%3] %%asi, %2, %0\n"
+ "\n1: casa [%4] %%asi, %3, %1\n"
"2:\n"
" .section .fixup,#alloc,#execinstr\n"
" .align 4\n"
"3: sethi %%hi(2b), %0\n"
" jmpl %0 + %%lo(2b), %%g0\n"
- " mov %4, %0\n"
+ " mov %5, %0\n"
" .previous\n"
" .section __ex_table,\"a\"\n"
" .align 4\n"
" .word 1b, 3b\n"
" .previous\n"
- : "=r" (newval)
- : "0" (newval), "r" (oldval), "r" (uaddr), "i" (-EFAULT)
+ : "+r" (ret), "=r" (newval)
+ : "1" (newval), "r" (oldval), "r" (uaddr), "i" (-EFAULT)
: "memory");

- return newval;
+ *uval = newval;
+ return ret;
}

#endif /* !(_SPARC64_FUTEX_H) */
diff --git a/arch/tile/include/asm/futex.h b/arch/tile/include/asm/futex.h
index fe0d10d..664b20a 100644
--- a/arch/tile/include/asm/futex.h
+++ b/arch/tile/include/asm/futex.h
@@ -119,8 +119,8 @@ static inline int futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
return ret;
}

-static inline int futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval,
- int newval)
+static inline int futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr,
+ int oldval, int newval)
{
struct __get_user asm_ret;

@@ -128,7 +128,8 @@ static inline int futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval,
return -EFAULT;

asm_ret = futex_cmpxchg(uaddr, oldval, newval);
- return asm_ret.err ? asm_ret.err : asm_ret.val;
+ *uval = asm_ret.val;
+ return asm_ret.err;
}

#ifndef __tilegx__
diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
index 1f11ce4..884c0b5 100644
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -109,9 +109,10 @@ static inline int futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
return ret;
}

-static inline int futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval,
- int newval)
+static inline int futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr,
+ int oldval, int newval)
{
+ int ret = 0;

#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_BSWAP)
/* Real i386 machines have no cmpxchg instruction */
@@ -122,18 +123,19 @@ static inline int futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval,
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

- asm volatile("1:\t" LOCK_PREFIX "cmpxchgl %3, %1\n"
+ asm volatile("1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"
"2:\t.section .fixup, \"ax\"\n"
- "3:\tmov %2, %0\n"
+ "3:\tmov %3, %0\n"
"\tjmp 2b\n"
"\t.previous\n"
_ASM_EXTABLE(1b, 3b)
- : "=a" (oldval), "+m" (*uaddr)
- : "i" (-EFAULT), "r" (newval), "0" (oldval)
+ : "+r" (ret), "=a" (oldval), "+m" (*uaddr)
+ : "i" (-EFAULT), "r" (newval), "1" (oldval)
: "memory"
);

- return oldval;
+ *uval = oldval;
+ return ret;
}

#endif
diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
index 3c2344f..132bf52 100644
--- a/include/asm-generic/futex.h
+++ b/include/asm-generic/futex.h
@@ -48,7 +48,8 @@ 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)
{
return -ENOSYS;
}
diff --git a/kernel/futex.c b/kernel/futex.c
index 3184d3b..53b783f 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -381,15 +381,16 @@ static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb,
return NULL;
}

-static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
+static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr,
+ u32 uval, u32 newval)
{
- u32 curval;
+ int ret;

pagefault_disable();
- curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval);
pagefault_enable();

- return curval;
+ return ret;
}

static int get_futex_value_locked(u32 *dest, u32 __user *from)
@@ -688,9 +689,7 @@ retry:
if (set_waiters)
newval |= FUTEX_WAITERS;

- curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
-
- if (unlikely(curval == -EFAULT))
+ if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval)))
return -EFAULT;

/*
@@ -728,9 +727,7 @@ retry:
lock_taken = 1;
}

- curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
-
- if (unlikely(curval == -EFAULT))
+ if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
return -EFAULT;
if (unlikely(curval != uval))
goto retry;
@@ -843,9 +840,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)

newval = FUTEX_WAITERS | task_pid_vnr(new_owner);

- curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
-
- if (curval == -EFAULT)
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
ret = -EFAULT;
else if (curval != uval)
ret = -EINVAL;
@@ -880,10 +875,8 @@ static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
* There is no waiter, so we unlock the futex. The owner died
* bit has not to be preserved here. We are the owner:
*/
- oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
-
- if (oldval == -EFAULT)
- return oldval;
+ if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0))
+ return -EFAULT;
if (oldval != uval)
return -EAGAIN;

@@ -1578,9 +1571,7 @@ retry:
while (1) {
newval = (uval & FUTEX_OWNER_DIED) | newtid;

- curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
-
- if (curval == -EFAULT)
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
goto handle_fault;
if (curval == uval)
break;
@@ -2073,11 +2064,9 @@ retry:
* again. If it succeeds then we can return without waking
* anyone else up:
*/
- if (!(uval & FUTEX_OWNER_DIED))
- uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
-
-
- if (unlikely(uval == -EFAULT))
+ if (!(uval & FUTEX_OWNER_DIED) &&
+ unlikely(cmpxchg_futex_value_locked(&uval, uaddr,
+ task_pid_vnr(current), 0)))
goto pi_faulted;
/*
* Rare case: we managed to release the lock atomically,
@@ -2464,9 +2453,7 @@ retry:
* userspace.
*/
mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
- nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
-
- if (nval == -EFAULT)
+ if (futex_atomic_cmpxchg_inatomic(&nval, uaddr, uval, mval))
return -1;

if (nval != uval)
@@ -2679,8 +2666,7 @@ static int __init futex_init(void)
* implementation, the non-functional ones will return
* -ENOSYS.
*/
- curval = cmpxchg_futex_value_locked(NULL, 0, 0);
- if (curval == -EFAULT)
+ if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
futex_cmpxchg_enabled = 1;

for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
--
1.7.3.1


--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.


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