* [PATCH RFC 11/26] arm: Remove spin_unlock_wait() arch-specific definitions
[not found] <20170629235918.GA6445@linux.vnet.ibm.com>
@ 2017-06-30 0:01 ` Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 12/26] arm64: " Paul E. McKenney
1 sibling, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2017-06-30 0:01 UTC (permalink / raw)
To: linux-arm-kernel
There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair. This commit therefore removes the underlying arch-specific
arch_spin_unlock_wait().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/arm/include/asm/spinlock.h | 16 ----------------
1 file changed, 16 deletions(-)
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index 4bec45442072..c030143c18c6 100644
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -52,22 +52,6 @@ static inline void dsb_sev(void)
* memory.
*/
-static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
-{
- u16 owner = READ_ONCE(lock->tickets.owner);
-
- for (;;) {
- arch_spinlock_t tmp = READ_ONCE(*lock);
-
- if (tmp.tickets.owner == tmp.tickets.next ||
- tmp.tickets.owner != owner)
- break;
-
- wfe();
- }
- smp_acquire__after_ctrl_dep();
-}
-
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
static inline void arch_spin_lock(arch_spinlock_t *lock)
--
2.5.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH RFC 12/26] arm64: Remove spin_unlock_wait() arch-specific definitions
[not found] <20170629235918.GA6445@linux.vnet.ibm.com>
2017-06-30 0:01 ` [PATCH RFC 11/26] arm: Remove spin_unlock_wait() arch-specific definitions Paul E. McKenney
@ 2017-06-30 0:01 ` Paul E. McKenney
2017-06-30 9:20 ` Will Deacon
1 sibling, 1 reply; 4+ messages in thread
From: Paul E. McKenney @ 2017-06-30 0:01 UTC (permalink / raw)
To: linux-arm-kernel
There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair. This commit therefore removes the underlying arch-specific
arch_spin_unlock_wait().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/arm64/include/asm/spinlock.h | 58 ++++-----------------------------------
1 file changed, 5 insertions(+), 53 deletions(-)
diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index cae331d553f8..f445bd7f2b9f 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -26,58 +26,6 @@
* The memory barriers are implicit with the load-acquire and store-release
* instructions.
*/
-static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
-{
- unsigned int tmp;
- arch_spinlock_t lockval;
- u32 owner;
-
- /*
- * Ensure prior spin_lock operations to other locks have completed
- * on this CPU before we test whether "lock" is locked.
- */
- smp_mb();
- owner = READ_ONCE(lock->owner) << 16;
-
- asm volatile(
-" sevl\n"
-"1: wfe\n"
-"2: ldaxr %w0, %2\n"
- /* Is the lock free? */
-" eor %w1, %w0, %w0, ror #16\n"
-" cbz %w1, 3f\n"
- /* Lock taken -- has there been a subsequent unlock->lock transition? */
-" eor %w1, %w3, %w0, lsl #16\n"
-" cbz %w1, 1b\n"
- /*
- * The owner has been updated, so there was an unlock->lock
- * transition that we missed. That means we can rely on the
- * store-release of the unlock operation paired with the
- * load-acquire of the lock operation to publish any of our
- * previous stores to the new lock owner and therefore don't
- * need to bother with the writeback below.
- */
-" b 4f\n"
-"3:\n"
- /*
- * Serialise against any concurrent lockers by writing back the
- * unlocked lock value
- */
- ARM64_LSE_ATOMIC_INSN(
- /* LL/SC */
-" stxr %w1, %w0, %2\n"
- __nops(2),
- /* LSE atomics */
-" mov %w1, %w0\n"
-" cas %w0, %w0, %2\n"
-" eor %w1, %w1, %w0\n")
- /* Somebody else wrote to the lock, GOTO 10 and reload the value */
-" cbnz %w1, 2b\n"
-"4:"
- : "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
- : "r" (owner)
- : "memory");
-}
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
@@ -176,7 +124,11 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
- smp_mb(); /* See arch_spin_unlock_wait */
+ /*
+ * Ensure prior spin_lock operations to other locks have completed
+ * on this CPU before we test whether "lock" is locked.
+ */
+ smp_mb(); /* ^^^ */
return !arch_spin_value_unlocked(READ_ONCE(*lock));
}
--
2.5.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH RFC 12/26] arm64: Remove spin_unlock_wait() arch-specific definitions
2017-06-30 0:01 ` [PATCH RFC 12/26] arm64: " Paul E. McKenney
@ 2017-06-30 9:20 ` Will Deacon
2017-06-30 17:29 ` Paul E. McKenney
0 siblings, 1 reply; 4+ messages in thread
From: Will Deacon @ 2017-06-30 9:20 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jun 29, 2017 at 05:01:20PM -0700, Paul E. McKenney wrote:
> There is no agreed-upon definition of spin_unlock_wait()'s semantics,
> and it appears that all callers could do just as well with a lock/unlock
> pair. This commit therefore removes the underlying arch-specific
> arch_spin_unlock_wait().
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: <linux-arm-kernel@lists.infradead.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Cc: Andrea Parri <parri.andrea@gmail.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> ---
> arch/arm64/include/asm/spinlock.h | 58 ++++-----------------------------------
> 1 file changed, 5 insertions(+), 53 deletions(-)
I'm going to miss this code.
Acked-by: Will Deacon <will.deacon@arm.com>
Will
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH RFC 12/26] arm64: Remove spin_unlock_wait() arch-specific definitions
2017-06-30 9:20 ` Will Deacon
@ 2017-06-30 17:29 ` Paul E. McKenney
0 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2017-06-30 17:29 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Jun 30, 2017 at 10:20:57AM +0100, Will Deacon wrote:
> On Thu, Jun 29, 2017 at 05:01:20PM -0700, Paul E. McKenney wrote:
> > There is no agreed-upon definition of spin_unlock_wait()'s semantics,
> > and it appears that all callers could do just as well with a lock/unlock
> > pair. This commit therefore removes the underlying arch-specific
> > arch_spin_unlock_wait().
> >
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will.deacon@arm.com>
> > Cc: <linux-arm-kernel@lists.infradead.org>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Alan Stern <stern@rowland.harvard.edu>
> > Cc: Andrea Parri <parri.andrea@gmail.com>
> > Cc: Linus Torvalds <torvalds@linux-foundation.org>
> > ---
> > arch/arm64/include/asm/spinlock.h | 58 ++++-----------------------------------
> > 1 file changed, 5 insertions(+), 53 deletions(-)
>
> I'm going to miss this code.
;-) ;-) ;-)
> Acked-by: Will Deacon <will.deacon@arm.com>
Applied, thank you!
Thanx, Paul
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-06-30 0:01 ` [PATCH RFC 11/26] arm: Remove spin_unlock_wait() arch-specific definitions Paul E. McKenney
2017-06-30 0:01 ` [PATCH RFC 12/26] arm64: " Paul E. McKenney
2017-06-30 9:20 ` Will Deacon
2017-06-30 17:29 ` Paul E. McKenney
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