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authorLinus Torvalds <torvalds@linux-foundation.org>2011-01-20 17:02:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-20 17:02:14 -0800
commit8d99641f6c1af806cd5d9e6badce91910219a161 (patch)
treeee841f807005a4a6234f6f502a13185d13a34870 /kernel
parentfc887b15d935ead2a00aef5779a18034e7c69ee1 (diff)
parent225c8e010f2d17a62aef131e24c6e7c111f36f9b (diff)
downloadlinux-linaro-precise-8d99641f6c1af806cd5d9e6badce91910219a161.tar.gz
Merge branch 'akpm'
* akpm: kernel/smp.c: consolidate writes in smp_call_function_interrupt() kernel/smp.c: fix smp_call_function_many() SMP race memcg: correctly order reading PCG_USED and pc->mem_cgroup backlight: fix 88pm860x_bl macro collision drivers/leds/ledtrig-gpio.c: make output match input, tighten input checking MAINTAINERS: update Atmel AT91 entry mm: fix truncate_setsize() comment memcg: fix rmdir, force_empty with THP memcg: fix LRU accounting with THP memcg: fix USED bit handling at uncharge in THP memcg: modify accounting function for supporting THP better fs/direct-io.c: don't try to allocate more than BIO_MAX_PAGES in a bio mm: compaction: prevent division-by-zero during user-requested compaction mm/vmscan.c: remove duplicate include of compaction.h memblock: fix memblock_is_region_memory() thp: keep highpte mapped until it is no longer needed kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT
Diffstat (limited to 'kernel')
-rw-r--r--kernel/smp.c51
1 files changed, 45 insertions, 6 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index 4ec30e06998..2fe66f7c617 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -194,23 +194,52 @@ void generic_smp_call_function_interrupt(void)
*/
list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
int refs;
+ void (*func) (void *info);
- if (!cpumask_test_and_clear_cpu(cpu, data->cpumask))
+ /*
+ * Since we walk the list without any locks, we might
+ * see an entry that was completed, removed from the
+ * list and is in the process of being reused.
+ *
+ * We must check that the cpu is in the cpumask before
+ * checking the refs, and both must be set before
+ * executing the callback on this cpu.
+ */
+
+ if (!cpumask_test_cpu(cpu, data->cpumask))
continue;
+ smp_rmb();
+
+ if (atomic_read(&data->refs) == 0)
+ continue;
+
+ func = data->csd.func; /* for later warn */
data->csd.func(data->csd.info);
+ /*
+ * If the cpu mask is not still set then it enabled interrupts,
+ * we took another smp interrupt, and executed the function
+ * twice on this cpu. In theory that copy decremented refs.
+ */
+ if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) {
+ WARN(1, "%pS enabled interrupts and double executed\n",
+ func);
+ continue;
+ }
+
refs = atomic_dec_return(&data->refs);
WARN_ON(refs < 0);
- if (!refs) {
- raw_spin_lock(&call_function.lock);
- list_del_rcu(&data->csd.list);
- raw_spin_unlock(&call_function.lock);
- }
if (refs)
continue;
+ WARN_ON(!cpumask_empty(data->cpumask));
+
+ raw_spin_lock(&call_function.lock);
+ list_del_rcu(&data->csd.list);
+ raw_spin_unlock(&call_function.lock);
+
csd_unlock(&data->csd);
}
@@ -454,11 +483,21 @@ void smp_call_function_many(const struct cpumask *mask,
data = &__get_cpu_var(cfd_data);
csd_lock(&data->csd);
+ BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask));
data->csd.func = func;
data->csd.info = info;
cpumask_and(data->cpumask, mask, cpu_online_mask);
cpumask_clear_cpu(this_cpu, data->cpumask);
+
+ /*
+ * To ensure the interrupt handler gets an complete view
+ * we order the cpumask and refs writes and order the read
+ * of them in the interrupt handler. In addition we may
+ * only clear our own cpu bit from the mask.
+ */
+ smp_wmb();
+
atomic_set(&data->refs, cpumask_weight(data->cpumask));
raw_spin_lock_irqsave(&call_function.lock, flags);