726328d92a
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) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> 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 <mingo@kernel.org>
230 lines
4.5 KiB
C
230 lines
4.5 KiB
C
/* spinlock.h: 64-bit Sparc spinlock support.
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*
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* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
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*/
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#ifndef __SPARC64_SPINLOCK_H
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#define __SPARC64_SPINLOCK_H
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#ifndef __ASSEMBLY__
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#include <asm/processor.h>
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#include <asm/barrier.h>
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/* To get debugging spinlocks which detect and catch
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* deadlock situations, set CONFIG_DEBUG_SPINLOCK
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* and rebuild your kernel.
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*/
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/* Because we play games to save cycles in the non-contention case, we
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* need to be extra careful about branch targets into the "spinning"
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* code. They live in their own section, but the newer V9 branches
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* have a shorter range than the traditional 32-bit sparc branch
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* variants. The rule is that the branches that go into and out of
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* the spinner sections must be pre-V9 branches.
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*/
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#define arch_spin_is_locked(lp) ((lp)->lock != 0)
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static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
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{
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smp_cond_load_acquire(&lock->lock, !VAL);
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}
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static inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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unsigned long tmp;
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__asm__ __volatile__(
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"1: ldstub [%1], %0\n"
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" brnz,pn %0, 2f\n"
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" nop\n"
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" .subsection 2\n"
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"2: ldub [%1], %0\n"
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" brnz,pt %0, 2b\n"
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" nop\n"
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" ba,a,pt %%xcc, 1b\n"
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" .previous"
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: "=&r" (tmp)
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: "r" (lock)
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: "memory");
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}
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static inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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unsigned long result;
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__asm__ __volatile__(
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" ldstub [%1], %0\n"
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: "=r" (result)
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: "r" (lock)
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: "memory");
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return (result == 0UL);
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}
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static inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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__asm__ __volatile__(
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" stb %%g0, [%0]"
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: /* No outputs */
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: "r" (lock)
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: "memory");
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}
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static inline void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
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{
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unsigned long tmp1, tmp2;
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__asm__ __volatile__(
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"1: ldstub [%2], %0\n"
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" brnz,pn %0, 2f\n"
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" nop\n"
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" .subsection 2\n"
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"2: rdpr %%pil, %1\n"
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" wrpr %3, %%pil\n"
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"3: ldub [%2], %0\n"
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" brnz,pt %0, 3b\n"
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" nop\n"
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" ba,pt %%xcc, 1b\n"
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" wrpr %1, %%pil\n"
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" .previous"
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: "=&r" (tmp1), "=&r" (tmp2)
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: "r"(lock), "r"(flags)
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: "memory");
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}
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/* Multi-reader locks, these are much saner than the 32-bit Sparc ones... */
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static void inline arch_read_lock(arch_rwlock_t *lock)
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{
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unsigned long tmp1, tmp2;
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__asm__ __volatile__ (
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"1: ldsw [%2], %0\n"
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" brlz,pn %0, 2f\n"
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"4: add %0, 1, %1\n"
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" cas [%2], %0, %1\n"
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" cmp %0, %1\n"
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" bne,pn %%icc, 1b\n"
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" nop\n"
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" .subsection 2\n"
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"2: ldsw [%2], %0\n"
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" brlz,pt %0, 2b\n"
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" nop\n"
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" ba,a,pt %%xcc, 4b\n"
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" .previous"
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: "=&r" (tmp1), "=&r" (tmp2)
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: "r" (lock)
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: "memory");
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}
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static int inline arch_read_trylock(arch_rwlock_t *lock)
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{
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int tmp1, tmp2;
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__asm__ __volatile__ (
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"1: ldsw [%2], %0\n"
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" brlz,a,pn %0, 2f\n"
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" mov 0, %0\n"
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" add %0, 1, %1\n"
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" cas [%2], %0, %1\n"
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" cmp %0, %1\n"
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" bne,pn %%icc, 1b\n"
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" mov 1, %0\n"
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"2:"
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: "=&r" (tmp1), "=&r" (tmp2)
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: "r" (lock)
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: "memory");
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return tmp1;
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}
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static void inline arch_read_unlock(arch_rwlock_t *lock)
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{
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unsigned long tmp1, tmp2;
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__asm__ __volatile__(
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"1: lduw [%2], %0\n"
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" sub %0, 1, %1\n"
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" cas [%2], %0, %1\n"
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" cmp %0, %1\n"
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" bne,pn %%xcc, 1b\n"
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" nop"
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: "=&r" (tmp1), "=&r" (tmp2)
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: "r" (lock)
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: "memory");
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}
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static void inline arch_write_lock(arch_rwlock_t *lock)
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{
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unsigned long mask, tmp1, tmp2;
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mask = 0x80000000UL;
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__asm__ __volatile__(
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"1: lduw [%2], %0\n"
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" brnz,pn %0, 2f\n"
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"4: or %0, %3, %1\n"
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" cas [%2], %0, %1\n"
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" cmp %0, %1\n"
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" bne,pn %%icc, 1b\n"
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" nop\n"
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" .subsection 2\n"
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"2: lduw [%2], %0\n"
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" brnz,pt %0, 2b\n"
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" nop\n"
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" ba,a,pt %%xcc, 4b\n"
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" .previous"
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: "=&r" (tmp1), "=&r" (tmp2)
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: "r" (lock), "r" (mask)
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: "memory");
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}
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static void inline arch_write_unlock(arch_rwlock_t *lock)
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{
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__asm__ __volatile__(
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" stw %%g0, [%0]"
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: /* no outputs */
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: "r" (lock)
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: "memory");
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}
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static int inline arch_write_trylock(arch_rwlock_t *lock)
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{
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unsigned long mask, tmp1, tmp2, result;
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mask = 0x80000000UL;
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__asm__ __volatile__(
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" mov 0, %2\n"
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"1: lduw [%3], %0\n"
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" brnz,pn %0, 2f\n"
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" or %0, %4, %1\n"
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" cas [%3], %0, %1\n"
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" cmp %0, %1\n"
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" bne,pn %%icc, 1b\n"
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" nop\n"
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" mov 1, %2\n"
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"2:"
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: "=&r" (tmp1), "=&r" (tmp2), "=&r" (result)
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: "r" (lock), "r" (mask)
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: "memory");
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return result;
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}
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#define arch_read_lock_flags(p, f) arch_read_lock(p)
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#define arch_write_lock_flags(p, f) arch_write_lock(p)
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#define arch_read_can_lock(rw) (!((rw)->lock & 0x80000000UL))
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#define arch_write_can_lock(rw) (!(rw)->lock)
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#define arch_spin_relax(lock) cpu_relax()
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#define arch_read_relax(lock) cpu_relax()
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#define arch_write_relax(lock) cpu_relax()
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#endif /* !(__ASSEMBLY__) */
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#endif /* !(__SPARC64_SPINLOCK_H) */
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