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authorVineet Gupta <vgupta@synopsys.com>2015-08-06 19:11:06 +0530
committerVineet Gupta <vgupta@synopsys.com>2015-08-20 18:16:01 +0530
commiteb2cd8b72b08fe56998600aee8a5dff93f7be5a2 (patch)
treef16645c5a57ce9221e2c6ced11b73789ea9d242c /arch/arc
parent5e0574292ad48dcdf48ef90a47da862c21d649a6 (diff)
downloadop-kernel-dev-eb2cd8b72b08fe56998600aee8a5dff93f7be5a2.zip
op-kernel-dev-eb2cd8b72b08fe56998600aee8a5dff93f7be5a2.tar.gz
ARC: ensure futex ops are atomic in !LLSC config
W/o hardware assisted atomic r-m-w the best we can do is to disable preemption. Cc: David Hildenbrand <dahi@linux.vnet.ibm.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Michel Lespinasse <walken@google.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/include/asm/futex.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arc/include/asm/futex.h b/arch/arc/include/asm/futex.h
index 0ea8bcc..8f44998 100644
--- a/arch/arc/include/asm/futex.h
+++ b/arch/arc/include/asm/futex.h
@@ -87,6 +87,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;
+#ifndef CONFIG_ARC_HAS_LLSC
+ preempt_disable(); /* to guarantee atomic r-m-w of futex op */
+#endif
pagefault_disable();
switch (op) {
@@ -111,6 +114,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
}
pagefault_enable();
+#ifndef CONFIG_ARC_HAS_LLSC
+ preempt_enable();
+#endif
if (!ret) {
switch (cmp) {
@@ -153,6 +159,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval,
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
+#ifndef CONFIG_ARC_HAS_LLSC
+ preempt_disable(); /* to guarantee atomic r-m-w of futex op */
+#endif
smp_mb();
__asm__ __volatile__(
@@ -182,6 +191,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval,
smp_mb();
+#ifndef CONFIG_ARC_HAS_LLSC
+ preempt_enable();
+#endif
*uval = existval;
return ret;
}
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