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Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar: "Two fixes: an smp-call fix and a lockdep fix" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: smp: Fix smp_call_function_single_async() locking lockdep: Make print_lock() robust against concurrent release
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commit
396c9df223
@ -551,7 +551,21 @@ static void print_lockdep_cache(struct lockdep_map *lock)
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static void print_lock(struct held_lock *hlock)
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{
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print_lock_name(hlock_class(hlock));
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/*
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* We can be called locklessly through debug_show_all_locks() so be
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* extra careful, the hlock might have been released and cleared.
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*/
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unsigned int class_idx = hlock->class_idx;
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/* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */
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barrier();
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if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
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printk("<RELEASED>\n");
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return;
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}
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print_lock_name(lock_classes + class_idx - 1);
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printk(", at: ");
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print_ip_sym(hlock->acquire_ip);
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}
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78
kernel/smp.c
78
kernel/smp.c
@ -19,7 +19,7 @@
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enum {
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CSD_FLAG_LOCK = 0x01,
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CSD_FLAG_WAIT = 0x02,
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CSD_FLAG_SYNCHRONOUS = 0x02,
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};
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struct call_function_data {
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@ -107,7 +107,7 @@ void __init call_function_init(void)
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*/
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static void csd_lock_wait(struct call_single_data *csd)
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{
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while (csd->flags & CSD_FLAG_LOCK)
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while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
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cpu_relax();
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}
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@ -121,19 +121,17 @@ static void csd_lock(struct call_single_data *csd)
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* to ->flags with any subsequent assignments to other
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* fields of the specified call_single_data structure:
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*/
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smp_mb();
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smp_wmb();
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}
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static void csd_unlock(struct call_single_data *csd)
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{
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WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
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WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
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/*
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* ensure we're all done before releasing data:
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*/
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smp_mb();
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csd->flags &= ~CSD_FLAG_LOCK;
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smp_store_release(&csd->flags, 0);
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}
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static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
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@ -144,13 +142,16 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
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* ->func, ->info, and ->flags set.
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*/
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static int generic_exec_single(int cpu, struct call_single_data *csd,
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smp_call_func_t func, void *info, int wait)
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smp_call_func_t func, void *info)
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{
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struct call_single_data csd_stack = { .flags = 0 };
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unsigned long flags;
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if (cpu == smp_processor_id()) {
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unsigned long flags;
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/*
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* We can unlock early even for the synchronous on-stack case,
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* since we're doing this from the same CPU..
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*/
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csd_unlock(csd);
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local_irq_save(flags);
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func(info);
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local_irq_restore(flags);
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@ -161,21 +162,9 @@ static int generic_exec_single(int cpu, struct call_single_data *csd,
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if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu))
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return -ENXIO;
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if (!csd) {
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csd = &csd_stack;
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if (!wait)
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csd = this_cpu_ptr(&csd_data);
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}
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csd_lock(csd);
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csd->func = func;
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csd->info = info;
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if (wait)
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csd->flags |= CSD_FLAG_WAIT;
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/*
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* The list addition should be visible before sending the IPI
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* handler locks the list to pull the entry off it because of
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@ -190,9 +179,6 @@ static int generic_exec_single(int cpu, struct call_single_data *csd,
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if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
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arch_send_call_function_single_ipi(cpu);
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if (wait)
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csd_lock_wait(csd);
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return 0;
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}
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@ -250,8 +236,17 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
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}
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llist_for_each_entry_safe(csd, csd_next, entry, llist) {
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csd->func(csd->info);
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csd_unlock(csd);
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smp_call_func_t func = csd->func;
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void *info = csd->info;
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/* Do we wait until *after* callback? */
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if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
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func(info);
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csd_unlock(csd);
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} else {
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csd_unlock(csd);
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func(info);
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}
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}
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/*
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@ -274,6 +269,8 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
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int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
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int wait)
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{
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struct call_single_data *csd;
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struct call_single_data csd_stack = { .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS };
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int this_cpu;
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int err;
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@ -292,7 +289,16 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
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WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
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&& !oops_in_progress);
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err = generic_exec_single(cpu, NULL, func, info, wait);
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csd = &csd_stack;
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if (!wait) {
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csd = this_cpu_ptr(&csd_data);
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csd_lock(csd);
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}
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err = generic_exec_single(cpu, csd, func, info);
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if (wait)
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csd_lock_wait(csd);
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put_cpu();
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@ -321,7 +327,15 @@ int smp_call_function_single_async(int cpu, struct call_single_data *csd)
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int err = 0;
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preempt_disable();
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err = generic_exec_single(cpu, csd, csd->func, csd->info, 0);
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/* We could deadlock if we have to wait here with interrupts disabled! */
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if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
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csd_lock_wait(csd);
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csd->flags = CSD_FLAG_LOCK;
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smp_wmb();
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err = generic_exec_single(cpu, csd, csd->func, csd->info);
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preempt_enable();
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return err;
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@ -433,6 +447,8 @@ void smp_call_function_many(const struct cpumask *mask,
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struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
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csd_lock(csd);
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if (wait)
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csd->flags |= CSD_FLAG_SYNCHRONOUS;
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csd->func = func;
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csd->info = info;
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llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));
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