![Ingo Molnar](/assets/img/avatar_default.png)
This patch implements a number of smp_processor_id() cleanup ideas that Arjan van de Ven and I came up with. The previous __smp_processor_id/_smp_processor_id/smp_processor_id API spaghetti was hard to follow both on the implementational and on the usage side. Some of the complexity arose from picking wrong names, some of the complexity comes from the fact that not all architectures defined __smp_processor_id. In the new code, there are two externally visible symbols: - smp_processor_id(): debug variant. - raw_smp_processor_id(): nondebug variant. Replaces all existing uses of _smp_processor_id() and __smp_processor_id(). Defined by every SMP architecture in include/asm-*/smp.h. There is one new internal symbol, dependent on DEBUG_PREEMPT: - debug_smp_processor_id(): internal debug variant, mapped to smp_processor_id(). Also, i moved debug_smp_processor_id() from lib/kernel_lock.c into a new lib/smp_processor_id.c file. All related comments got updated and/or clarified. I have build/boot tested the following 8 .config combinations on x86: {SMP,UP} x {PREEMPT,!PREEMPT} x {DEBUG_PREEMPT,!DEBUG_PREEMPT} I have also build/boot tested x64 on UP/PREEMPT/DEBUG_PREEMPT. (Other architectures are untested, but should work just fine.) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
191 lines
4 KiB
C
191 lines
4 KiB
C
/*
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* Locks for smp ppc
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*
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* Written by Cort Dougan (cort@cs.nmt.edu)
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*/
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#include <linux/config.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/module.h>
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#include <asm/ppc_asm.h>
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#include <asm/smp.h>
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#ifdef CONFIG_DEBUG_SPINLOCK
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#undef INIT_STUCK
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#define INIT_STUCK 200000000 /*0xffffffff*/
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/*
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* Try to acquire a spinlock.
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* Only does the stwcx. if the load returned 0 - the Programming
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* Environments Manual suggests not doing unnecessary stcwx.'s
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* since they may inhibit forward progress by other CPUs in getting
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* a lock.
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*/
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static inline unsigned long __spin_trylock(volatile unsigned long *lock)
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{
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unsigned long ret;
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__asm__ __volatile__ ("\n\
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1: lwarx %0,0,%1\n\
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cmpwi 0,%0,0\n\
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bne 2f\n"
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PPC405_ERR77(0,%1)
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" stwcx. %2,0,%1\n\
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bne- 1b\n\
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isync\n\
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2:"
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: "=&r"(ret)
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: "r"(lock), "r"(1)
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: "cr0", "memory");
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return ret;
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}
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void _raw_spin_lock(spinlock_t *lock)
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{
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int cpu = smp_processor_id();
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unsigned int stuck = INIT_STUCK;
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while (__spin_trylock(&lock->lock)) {
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while ((unsigned volatile long)lock->lock != 0) {
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if (!--stuck) {
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printk("_spin_lock(%p) CPU#%d NIP %p"
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" holder: cpu %ld pc %08lX\n",
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lock, cpu, __builtin_return_address(0),
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lock->owner_cpu,lock->owner_pc);
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stuck = INIT_STUCK;
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/* steal the lock */
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/*xchg_u32((void *)&lock->lock,0);*/
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}
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}
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}
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lock->owner_pc = (unsigned long)__builtin_return_address(0);
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lock->owner_cpu = cpu;
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}
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EXPORT_SYMBOL(_raw_spin_lock);
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int _raw_spin_trylock(spinlock_t *lock)
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{
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if (__spin_trylock(&lock->lock))
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return 0;
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lock->owner_cpu = smp_processor_id();
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lock->owner_pc = (unsigned long)__builtin_return_address(0);
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return 1;
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}
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EXPORT_SYMBOL(_raw_spin_trylock);
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void _raw_spin_unlock(spinlock_t *lp)
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{
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if ( !lp->lock )
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printk("_spin_unlock(%p): no lock cpu %d curr PC %p %s/%d\n",
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lp, smp_processor_id(), __builtin_return_address(0),
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current->comm, current->pid);
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if ( lp->owner_cpu != smp_processor_id() )
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printk("_spin_unlock(%p): cpu %d trying clear of cpu %d pc %lx val %lx\n",
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lp, smp_processor_id(), (int)lp->owner_cpu,
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lp->owner_pc,lp->lock);
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lp->owner_pc = lp->owner_cpu = 0;
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wmb();
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lp->lock = 0;
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}
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EXPORT_SYMBOL(_raw_spin_unlock);
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/*
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* For rwlocks, zero is unlocked, -1 is write-locked,
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* positive is read-locked.
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*/
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static __inline__ int __read_trylock(rwlock_t *rw)
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{
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signed int tmp;
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__asm__ __volatile__(
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"2: lwarx %0,0,%1 # __read_trylock\n\
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addic. %0,%0,1\n\
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ble- 1f\n"
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PPC405_ERR77(0,%1)
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" stwcx. %0,0,%1\n\
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bne- 2b\n\
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isync\n\
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1:"
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: "=&r"(tmp)
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: "r"(&rw->lock)
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: "cr0", "memory");
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return tmp;
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}
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int _raw_read_trylock(rwlock_t *rw)
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{
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return __read_trylock(rw) > 0;
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}
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EXPORT_SYMBOL(_raw_read_trylock);
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void _raw_read_lock(rwlock_t *rw)
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{
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unsigned int stuck;
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while (__read_trylock(rw) <= 0) {
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stuck = INIT_STUCK;
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while (!read_can_lock(rw)) {
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if (--stuck == 0) {
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printk("_read_lock(%p) CPU#%d lock %d\n",
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rw, raw_smp_processor_id(), rw->lock);
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stuck = INIT_STUCK;
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}
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}
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}
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}
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EXPORT_SYMBOL(_raw_read_lock);
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void _raw_read_unlock(rwlock_t *rw)
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{
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if ( rw->lock == 0 )
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printk("_read_unlock(): %s/%d (nip %08lX) lock %d\n",
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current->comm,current->pid,current->thread.regs->nip,
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rw->lock);
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wmb();
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atomic_dec((atomic_t *) &(rw)->lock);
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}
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EXPORT_SYMBOL(_raw_read_unlock);
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void _raw_write_lock(rwlock_t *rw)
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{
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unsigned int stuck;
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while (cmpxchg(&rw->lock, 0, -1) != 0) {
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stuck = INIT_STUCK;
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while (!write_can_lock(rw)) {
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if (--stuck == 0) {
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printk("write_lock(%p) CPU#%d lock %d)\n",
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rw, raw_smp_processor_id(), rw->lock);
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stuck = INIT_STUCK;
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}
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}
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}
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wmb();
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}
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EXPORT_SYMBOL(_raw_write_lock);
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int _raw_write_trylock(rwlock_t *rw)
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{
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if (cmpxchg(&rw->lock, 0, -1) != 0)
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return 0;
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wmb();
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return 1;
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}
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EXPORT_SYMBOL(_raw_write_trylock);
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void _raw_write_unlock(rwlock_t *rw)
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{
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if (rw->lock >= 0)
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printk("_write_lock(): %s/%d (nip %08lX) lock %d\n",
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current->comm,current->pid,current->thread.regs->nip,
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rw->lock);
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wmb();
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rw->lock = 0;
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}
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EXPORT_SYMBOL(_raw_write_unlock);
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#endif
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