| Message ID | 1498780894-8253-12-git-send-email-paulmck@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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
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
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)); }
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(-)