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Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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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
This commit is contained in:
Linus Torvalds 2015-04-18 11:23:42 -04:00
parent 8f502d5b9e 8053871d0f
commit 396c9df223
2 changed files with 62 additions and 32 deletions
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16
kernel/locking/lockdep.c
View file

@ -551,7 +551,21 @@ static void print_lockdep_cache(struct lockdep_map *lock)
static void print_lock(struct held_lock *hlock)
{
print_lock_name(hlock_class(hlock));
/*
* We can be called locklessly through debug_show_all_locks() so be
* extra careful, the hlock might have been released and cleared.
*/
unsigned int class_idx = hlock->class_idx;
/* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */
barrier();
if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
printk("<RELEASED>\n");
return;
}
print_lock_name(lock_classes + class_idx - 1);
printk(", at: ");
print_ip_sym(hlock->acquire_ip);
}

78
kernel/smp.c
View file

@ -19,7 +19,7 @@
enum {
CSD_FLAG_LOCK = 0x01,
CSD_FLAG_WAIT = 0x02,
CSD_FLAG_SYNCHRONOUS = 0x02,
};
struct call_function_data {
@ -107,7 +107,7 @@ void __init call_function_init(void)
*/
static void csd_lock_wait(struct call_single_data *csd)
{
while (csd->flags & CSD_FLAG_LOCK)
while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
cpu_relax();
}
@ -121,19 +121,17 @@ static void csd_lock(struct call_single_data *csd)
* to ->flags with any subsequent assignments to other
* fields of the specified call_single_data structure:
*/
smp_mb();
smp_wmb();
}
static void csd_unlock(struct call_single_data *csd)
{
WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
/*
* ensure we're all done before releasing data:
*/
smp_mb();
csd->flags &= ~CSD_FLAG_LOCK;
smp_store_release(&csd->flags, 0);
}
static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
@ -144,13 +142,16 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
* ->func, ->info, and ->flags set.
*/
static int generic_exec_single(int cpu, struct call_single_data *csd,
smp_call_func_t func, void *info, int wait)
smp_call_func_t func, void *info)
{
struct call_single_data csd_stack = { .flags = 0 };
unsigned long flags;
if (cpu == smp_processor_id()) {
unsigned long flags;
/*
* We can unlock early even for the synchronous on-stack case,
* since we're doing this from the same CPU..
*/
csd_unlock(csd);
local_irq_save(flags);
func(info);
local_irq_restore(flags);
@ -161,21 +162,9 @@ static int generic_exec_single(int cpu, struct call_single_data *csd,
if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu))
return -ENXIO;
if (!csd) {
csd = &csd_stack;
if (!wait)
csd = this_cpu_ptr(&csd_data);
}
csd_lock(csd);
csd->func = func;
csd->info = info;
if (wait)
csd->flags |= CSD_FLAG_WAIT;
/*
* The list addition should be visible before sending the IPI
* handler locks the list to pull the entry off it because of
@ -190,9 +179,6 @@ static int generic_exec_single(int cpu, struct call_single_data *csd,
if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
arch_send_call_function_single_ipi(cpu);
if (wait)
csd_lock_wait(csd);
return 0;
}
@ -250,8 +236,17 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
}
llist_for_each_entry_safe(csd, csd_next, entry, llist) {
csd->func(csd->info);
csd_unlock(csd);
smp_call_func_t func = csd->func;
void *info = csd->info;
/* Do we wait until *after* callback? */
if (csd->flags & CSD_FLAG_SYNCHRONOUS) {
func(info);
csd_unlock(csd);
} else {
csd_unlock(csd);
func(info);
}
}
/*
@ -274,6 +269,8 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
int wait)
{
struct call_single_data *csd;
struct call_single_data csd_stack = { .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS };
int this_cpu;
int err;
@ -292,7 +289,16 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
&& !oops_in_progress);
err = generic_exec_single(cpu, NULL, func, info, wait);
csd = &csd_stack;
if (!wait) {
csd = this_cpu_ptr(&csd_data);
csd_lock(csd);
}
err = generic_exec_single(cpu, csd, func, info);
if (wait)
csd_lock_wait(csd);
put_cpu();
@ -321,7 +327,15 @@ int smp_call_function_single_async(int cpu, struct call_single_data *csd)
int err = 0;
preempt_disable();
err = generic_exec_single(cpu, csd, csd->func, csd->info, 0);
/* We could deadlock if we have to wait here with interrupts disabled! */
if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK))
csd_lock_wait(csd);
csd->flags = CSD_FLAG_LOCK;
smp_wmb();
err = generic_exec_single(cpu, csd, csd->func, csd->info);
preempt_enable();
return err;
@ -433,6 +447,8 @@ void smp_call_function_many(const struct cpumask *mask,
struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
csd_lock(csd);
if (wait)
csd->flags |= CSD_FLAG_SYNCHRONOUS;
csd->func = func;
csd->info = info;
llist_add(&csd->llist, &per_cpu(call_single_queue, cpu));