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Date: Thu, 21 Aug 2008 17:29:48 -0700 From: Jeremy Fitzhardinge <jeremy@...p.org> To: Ingo Molnar <mingo@...e.hu> CC: Nick Piggin <nickpiggin@...oo.com.au>, Andi Kleen <andi@...stfloor.org>, "Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>, Suresh Siddha <suresh.b.siddha@...el.com>, Jens Axboe <jens.axboe@...cle.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Rusty Russell <rusty@...tcorp.com.au> Subject: [PATCH 1/2] smp_call_function: don't use lock in call_function_data 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@...rix.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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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