From 54fdade1c3332391948ec43530c02c4794a38172 Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Tue, 22 Sep 2009 16:43:39 -0700 Subject: generic-ipi: make struct call_function_data lockless This patch can remove spinlock from struct call_function_data, the reasons are below: 1: add a new interface for cpumask named cpumask_test_and_clear_cpu(), it can atomically test and clear specific cpu, we can use it instead of cpumask_test_cpu() and cpumask_clear_cpu() and no need data->lock to protect those in generic_smp_call_function_interrupt(). 2: in smp_call_function_many(), after csd_lock() return, the current's cfd_data is deleted from call_function list, so it not have race between other cpus, then cfs_data is only used in smp_call_function_many() that must disable preemption and not from a hardware interrupthandler or from a bottom half handler to call, only the correspond cpu can use it, so it not have race in current cpu, no need cfs_data->lock to protect it. 3: after 1 and 2, cfs_data->lock is only use to protect cfs_data->refs in generic_smp_call_function_interrupt(), so we can define cfs_data->refs to atomic_t, and no need cfs_data->lock any more. Signed-off-by: Xiao Guangrong Cc: Ingo Molnar Cc: Jens Axboe Cc: Nick Piggin Cc: Peter Zijlstra Acked-by: Rusty Russell [akpm@linux-foundation.org: use atomic_dec_return()] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpumask.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'include/linux/cpumask.h') diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 796df12091b7..9b1d458aac6e 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -714,6 +714,18 @@ static inline int cpumask_test_and_set_cpu(int cpu, struct cpumask *cpumask) return test_and_set_bit(cpumask_check(cpu), cpumask_bits(cpumask)); } +/** + * cpumask_test_and_clear_cpu - atomically test and clear a cpu in a cpumask + * @cpu: cpu number (< nr_cpu_ids) + * @cpumask: the cpumask pointer + * + * test_and_clear_bit wrapper for cpumasks. + */ +static inline int cpumask_test_and_clear_cpu(int cpu, struct cpumask *cpumask) +{ + return test_and_clear_bit(cpumask_check(cpu), cpumask_bits(cpumask)); +} + /** * cpumask_setall - set all cpus (< nr_cpu_ids) in a cpumask * @dstp: the cpumask pointer -- cgit v1.2.3-59-g8ed1b