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Commit eb2cd8b7 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

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: default avatarVineet Gupta <vgupta@synopsys.com>
parent 5e057429

arch/arc/include/asm/futex.h

+12 −0
Original line number Original line Diff line number Diff line
@@ -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)))

	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))

		return -EFAULT;

		return -EFAULT;





#ifndef CONFIG_ARC_HAS_LLSC

	preempt_disable();	/* to guarantee atomic r-m-w of futex op */

#endif

	pagefault_disable();

	pagefault_disable();





	switch (op) {

	switch (op) {
@@ -111,6 +114,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr) 
	}

	}





	pagefault_enable();

	pagefault_enable();

#ifndef CONFIG_ARC_HAS_LLSC

	preempt_enable();

#endif





	if (!ret) {

	if (!ret) {

		switch (cmp) {

		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)))

	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))

		return -EFAULT;

		return -EFAULT;





#ifndef CONFIG_ARC_HAS_LLSC

	preempt_disable();	/* to guarantee atomic r-m-w of futex op */

#endif

	smp_mb();

	smp_mb();





	__asm__ __volatile__(

	__asm__ __volatile__(
@@ -182,6 +191,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, 




	smp_mb();

	smp_mb();





#ifndef CONFIG_ARC_HAS_LLSC

	preempt_enable();

#endif

	*uval = existval;

	*uval = existval;

	return ret;

	return ret;

}

}