Messages in this thread Patch in this message | | | Date | Thu, 21 Aug 2008 17:29:48 -0700 | From | Jeremy Fitzhardinge <> | Subject | [PATCH 1/2] smp_call_function: don't use lock in call_function_data |
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There's no need for a lock in call_function_data, since it's only used to decrement-and-test a counter. Use an atomic instead.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- kernel/smp.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-)
=================================================================== --- a/kernel/smp.c +++ b/kernel/smp.c @@ -10,6 +10,7 @@ #include <linux/rcupdate.h> #include <linux/rculist.h> #include <linux/smp.h> +#include <asm/atomic.h> bool __read_mostly smp_single_ipi_queue = false; @@ -37,8 +38,7 @@ struct call_function_data { struct call_single_data csd; - spinlock_t lock; - unsigned int refs; + atomic_t refs; cpumask_t cpumask; struct rcu_head rcu_head; }; @@ -125,21 +125,13 @@ */ rcu_read_lock(); list_for_each_entry_rcu(data, &queue->list, csd.list) { - int refs; - if (!cpu_isset(cpu, data->cpumask)) continue; data->csd.func(data->csd.info); - spin_lock(&data->lock); cpu_clear(cpu, data->cpumask); - WARN_ON(data->refs == 0); - data->refs--; - refs = data->refs; - spin_unlock(&data->lock); - - if (refs) + if (!atomic_dec_and_test(&data->refs)) continue; spin_lock(&queue->lock); @@ -379,10 +371,9 @@ slowpath = 1; } - spin_lock_init(&data->lock); data->csd.func = func; data->csd.info = info; - data->refs = num_cpus; + atomic_set(&data->refs, num_cpus); data->cpumask = mask; spin_lock_irqsave(&queue->lock, flags);
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