![Rusty Russell](/assets/img/avatar_default.png)
It turns out that the most called ops, by several orders of magnitude, are the interrupt manipulation ops. These are obvious candidates for patching, so mark them up and create infrastructure for it. The method used is that the ops structure has a patch function, which is called for each place which needs to be patched: this returns a number of instructions (the rest are NOP-padded). Usually we can spare a register (%eax) for the binary patched code to use, but in a couple of critical places in entry.S we can't: we make the clobbers explicit at the call site, and manually clobber the allowed registers in debug mode as an extra check. And: Don't abuse CONFIG_DEBUG_KERNEL, add CONFIG_DEBUG_PARAVIRT. And: AK: Fix warnings in x86-64 alternative.c build And: AK: Fix compilation with defconfig And: ^From: Andrew Morton <akpm@osdl.org> Some binutlises still like to emit references to __stop_parainstructions and __start_parainstructions. And: AK: Fix warnings about unused variables when PARAVIRT is disabled. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org>
222 lines
5.1 KiB
C
222 lines
5.1 KiB
C
#ifndef __ASM_SPINLOCK_H
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#define __ASM_SPINLOCK_H
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#include <asm/atomic.h>
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#include <asm/rwlock.h>
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#include <asm/page.h>
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#include <asm/processor.h>
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#include <linux/compiler.h>
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#ifdef CONFIG_PARAVIRT
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#include <asm/paravirt.h>
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#else
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#define CLI_STRING "cli"
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#define STI_STRING "sti"
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#define CLI_STI_CLOBBERS
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#define CLI_STI_INPUT_ARGS
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#endif /* CONFIG_PARAVIRT */
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/*
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* Your basic SMP spinlocks, allowing only a single CPU anywhere
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*
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* Simple spin lock operations. There are two variants, one clears IRQ's
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* on the local processor, one does not.
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*
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* We make no fairness assumptions. They have a cost.
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*
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* (the type definitions are in asm/spinlock_types.h)
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*/
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static inline int __raw_spin_is_locked(raw_spinlock_t *x)
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{
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return *(volatile signed char *)(&(x)->slock) <= 0;
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}
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static inline void __raw_spin_lock(raw_spinlock_t *lock)
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{
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asm volatile("\n1:\t"
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LOCK_PREFIX " ; decb %0\n\t"
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"jns 3f\n"
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"2:\t"
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"rep;nop\n\t"
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"cmpb $0,%0\n\t"
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"jle 2b\n\t"
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"jmp 1b\n"
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"3:\n\t"
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: "+m" (lock->slock) : : "memory");
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}
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/*
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* It is easier for the lock validator if interrupts are not re-enabled
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* in the middle of a lock-acquire. This is a performance feature anyway
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* so we turn it off:
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*
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* NOTE: there's an irqs-on section here, which normally would have to be
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* irq-traced, but on CONFIG_TRACE_IRQFLAGS we never use this variant.
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*/
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#ifndef CONFIG_PROVE_LOCKING
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static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
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{
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asm volatile(
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"\n1:\t"
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LOCK_PREFIX " ; decb %[slock]\n\t"
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"jns 5f\n"
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"2:\t"
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"testl $0x200, %[flags]\n\t"
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"jz 4f\n\t"
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STI_STRING "\n"
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"3:\t"
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"rep;nop\n\t"
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"cmpb $0, %[slock]\n\t"
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"jle 3b\n\t"
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CLI_STRING "\n\t"
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"jmp 1b\n"
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"4:\t"
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"rep;nop\n\t"
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"cmpb $0, %[slock]\n\t"
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"jg 1b\n\t"
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"jmp 4b\n"
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"5:\n\t"
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: [slock] "+m" (lock->slock)
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: [flags] "r" (flags)
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CLI_STI_INPUT_ARGS
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: "memory" CLI_STI_CLOBBERS);
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}
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#endif
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static inline int __raw_spin_trylock(raw_spinlock_t *lock)
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{
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char oldval;
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asm volatile(
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"xchgb %b0,%1"
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:"=q" (oldval), "+m" (lock->slock)
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:"0" (0) : "memory");
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return oldval > 0;
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}
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/*
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* __raw_spin_unlock based on writing $1 to the low byte.
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* This method works. Despite all the confusion.
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* (except on PPro SMP or if we are using OOSTORE, so we use xchgb there)
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* (PPro errata 66, 92)
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*/
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#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)
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static inline void __raw_spin_unlock(raw_spinlock_t *lock)
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{
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asm volatile("movb $1,%0" : "+m" (lock->slock) :: "memory");
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}
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#else
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static inline void __raw_spin_unlock(raw_spinlock_t *lock)
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{
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char oldval = 1;
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asm volatile("xchgb %b0, %1"
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: "=q" (oldval), "+m" (lock->slock)
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: "0" (oldval) : "memory");
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}
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#endif
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static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
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{
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while (__raw_spin_is_locked(lock))
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cpu_relax();
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}
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/*
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* Read-write spinlocks, allowing multiple readers
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* but only one writer.
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*
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* NOTE! it is quite common to have readers in interrupts
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* but no interrupt writers. For those circumstances we
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* can "mix" irq-safe locks - any writer needs to get a
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* irq-safe write-lock, but readers can get non-irqsafe
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* read-locks.
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*
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* On x86, we implement read-write locks as a 32-bit counter
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* with the high bit (sign) being the "contended" bit.
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*
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* The inline assembly is non-obvious. Think about it.
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*
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* Changed to use the same technique as rw semaphores. See
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* semaphore.h for details. -ben
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*
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* the helpers are in arch/i386/kernel/semaphore.c
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*/
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/**
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* read_can_lock - would read_trylock() succeed?
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* @lock: the rwlock in question.
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*/
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static inline int __raw_read_can_lock(raw_rwlock_t *x)
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{
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return (int)(x)->lock > 0;
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}
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/**
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* write_can_lock - would write_trylock() succeed?
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* @lock: the rwlock in question.
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*/
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static inline int __raw_write_can_lock(raw_rwlock_t *x)
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{
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return (x)->lock == RW_LOCK_BIAS;
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}
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static inline void __raw_read_lock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX " subl $1,(%0)\n\t"
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"jns 1f\n"
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"call __read_lock_failed\n\t"
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"1:\n"
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::"a" (rw) : "memory");
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}
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static inline void __raw_write_lock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX " subl $" RW_LOCK_BIAS_STR ",(%0)\n\t"
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"jz 1f\n"
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"call __write_lock_failed\n\t"
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"1:\n"
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::"a" (rw) : "memory");
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}
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static inline int __raw_read_trylock(raw_rwlock_t *lock)
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{
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atomic_t *count = (atomic_t *)lock;
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atomic_dec(count);
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if (atomic_read(count) >= 0)
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return 1;
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atomic_inc(count);
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return 0;
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}
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static inline int __raw_write_trylock(raw_rwlock_t *lock)
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{
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atomic_t *count = (atomic_t *)lock;
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if (atomic_sub_and_test(RW_LOCK_BIAS, count))
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return 1;
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atomic_add(RW_LOCK_BIAS, count);
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return 0;
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}
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static inline void __raw_read_unlock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX "incl %0" :"+m" (rw->lock) : : "memory");
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}
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static inline void __raw_write_unlock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX "addl $" RW_LOCK_BIAS_STR ", %0"
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: "+m" (rw->lock) : : "memory");
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}
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#define _raw_spin_relax(lock) cpu_relax()
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#define _raw_read_relax(lock) cpu_relax()
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#define _raw_write_relax(lock) cpu_relax()
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#endif /* __ASM_SPINLOCK_H */
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