From 726328d92a42b6d4b76078e2659f43067f82c4e8 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 26 May 2016 10:35:03 +0200 Subject: locking/spinlock, arch: Update and fix spin_unlock_wait() implementations This patch updates/fixes all spin_unlock_wait() implementations. The update is in semantics; where it previously was only a control dependency, we now upgrade to a full load-acquire to match the store-release from the spin_unlock() we waited on. This ensures that when spin_unlock_wait() returns, we're guaranteed to observe the full critical section we waited on. This fixes a number of spin_unlock_wait() users that (not unreasonably) rely on this. I also fixed a number of ticket lock versions to only wait on the current lock holder, instead of for a full unlock, as this is sufficient. Furthermore; again for ticket locks; I added an smp_rmb() in between the initial ticket load and the spin loop testing the current value because I could not convince myself the address dependency is sufficient, esp. if the loads are of different sizes. I'm more than happy to remove this smp_rmb() again if people are certain the address dependency does indeed work as expected. Note: PPC32 will be fixed independently Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: chris@zankel.net Cc: cmetcalf@mellanox.com Cc: davem@davemloft.net Cc: dhowells@redhat.com Cc: james.hogan@imgtec.com Cc: jejb@parisc-linux.org Cc: linux@armlinux.org.uk Cc: mpe@ellerman.id.au Cc: ralf@linux-mips.org Cc: realmz6@gmail.com Cc: rkuo@codeaurora.org Cc: rth@twiddle.net Cc: schwidefsky@de.ibm.com Cc: tony.luck@intel.com Cc: vgupta@synopsys.com Cc: ysato@users.sourceforge.jp Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/xtensa/include/asm/spinlock.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'arch/xtensa') diff --git a/arch/xtensa/include/asm/spinlock.h b/arch/xtensa/include/asm/spinlock.h index 1d95fa5..a36221c 100644 --- a/arch/xtensa/include/asm/spinlock.h +++ b/arch/xtensa/include/asm/spinlock.h @@ -11,6 +11,9 @@ #ifndef _XTENSA_SPINLOCK_H #define _XTENSA_SPINLOCK_H +#include +#include + /* * spinlock * @@ -29,8 +32,11 @@ */ #define arch_spin_is_locked(x) ((x)->slock != 0) -#define arch_spin_unlock_wait(lock) \ - do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0) + +static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) +{ + smp_cond_load_acquire(&lock->slock, !VAL); +} #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) -- cgit v1.1 From 6dc25876cdb17fd3906504dcabb9e537f8433000 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 18 Apr 2016 01:16:03 +0200 Subject: locking/atomic, arch/xtensa: Implement atomic_fetch_{add,sub,and,or,xor}() Implement FETCH-OP atomic primitives, these are very similar to the existing OP-RETURN primitives we already have, except they return the value of the atomic variable _before_ modification. This is especially useful for irreversible operations -- such as bitops (because it becomes impossible to reconstruct the state prior to modification). Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Chris Zankel Cc: Linus Torvalds Cc: Max Filippov Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Signed-off-by: Ingo Molnar --- arch/xtensa/include/asm/atomic.h | 54 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 50 insertions(+), 4 deletions(-) (limited to 'arch/xtensa') diff --git a/arch/xtensa/include/asm/atomic.h b/arch/xtensa/include/asm/atomic.h index fd8017c..d95a8aa 100644 --- a/arch/xtensa/include/asm/atomic.h +++ b/arch/xtensa/include/asm/atomic.h @@ -98,6 +98,26 @@ static inline int atomic_##op##_return(int i, atomic_t * v) \ return result; \ } +#define ATOMIC_FETCH_OP(op) \ +static inline int atomic_fetch_##op(int i, atomic_t * v) \ +{ \ + unsigned long tmp; \ + int result; \ + \ + __asm__ __volatile__( \ + "1: l32i %1, %3, 0\n" \ + " wsr %1, scompare1\n" \ + " " #op " %0, %1, %2\n" \ + " s32c1i %0, %3, 0\n" \ + " bne %0, %1, 1b\n" \ + : "=&a" (result), "=&a" (tmp) \ + : "a" (i), "a" (v) \ + : "memory" \ + ); \ + \ + return result; \ +} + #else /* XCHAL_HAVE_S32C1I */ #define ATOMIC_OP(op) \ @@ -138,18 +158,44 @@ static inline int atomic_##op##_return(int i, atomic_t * v) \ return vval; \ } +#define ATOMIC_FETCH_OP(op) \ +static inline int atomic_fetch_##op(int i, atomic_t * v) \ +{ \ + unsigned int tmp, vval; \ + \ + __asm__ __volatile__( \ + " rsil a15,"__stringify(TOPLEVEL)"\n" \ + " l32i %0, %3, 0\n" \ + " " #op " %1, %0, %2\n" \ + " s32i %1, %3, 0\n" \ + " wsr a15, ps\n" \ + " rsync\n" \ + : "=&a" (vval), "=&a" (tmp) \ + : "a" (i), "a" (v) \ + : "a15", "memory" \ + ); \ + \ + return vval; \ +} + #endif /* XCHAL_HAVE_S32C1I */ -#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op) +#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op) ATOMIC_OP_RETURN(op) ATOMIC_OPS(add) ATOMIC_OPS(sub) -ATOMIC_OP(and) -ATOMIC_OP(or) -ATOMIC_OP(xor) +#undef ATOMIC_OPS +#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op) + +#define atomic_fetch_or atomic_fetch_or + +ATOMIC_OPS(and) +ATOMIC_OPS(or) +ATOMIC_OPS(xor) #undef ATOMIC_OPS +#undef ATOMIC_FETCH_OP #undef ATOMIC_OP_RETURN #undef ATOMIC_OP -- cgit v1.1 From b53d6bedbe781974097fd8c38263f6cc78ff9ea7 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 18 Apr 2016 00:58:25 +0200 Subject: locking/atomic: Remove linux/atomic.h:atomic_fetch_or() Since all architectures have this implemented now natively, remove this dead code. Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/xtensa/include/asm/atomic.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/xtensa') diff --git a/arch/xtensa/include/asm/atomic.h b/arch/xtensa/include/asm/atomic.h index d95a8aa..e7a23f2 100644 --- a/arch/xtensa/include/asm/atomic.h +++ b/arch/xtensa/include/asm/atomic.h @@ -188,8 +188,6 @@ ATOMIC_OPS(sub) #undef ATOMIC_OPS #define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op) -#define atomic_fetch_or atomic_fetch_or - ATOMIC_OPS(and) ATOMIC_OPS(or) ATOMIC_OPS(xor) -- cgit v1.1