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Commit b3a7e98e authored by Gilad Ben-Yossef's avatar Gilad Ben-Yossef Committed by Linus Torvalds
Browse files

smp: add func to IPI cpus based on parameter func 



Add the on_each_cpu_cond() function that wraps on_each_cpu_mask() and
calculates the cpumask of cpus to IPI by calling a function supplied as a
parameter in order to determine whether to IPI each specific cpu.

The function works around allocation failure of cpumask variable in
CONFIG_CPUMASK_OFFSTACK=y by itereating over cpus sending an IPI a time
via smp_call_function_single().

The function is useful since it allows to seperate the specific code that
decided in each case whether to IPI a specific cpu for a specific request
from the common boilerplate code of handling creating the mask, handling
failures etc.

[akpm@linux-foundation.org: s/gfpflags/gfp_flags/]
[akpm@linux-foundation.org: avoid double-evaluation of `info' (per Michal), parenthesise evaluation of `cond_func']
[akpm@linux-foundation.org: s/CPU/CPUs, use all 80 cols in comment]
Signed-off-by: default avatarGilad Ben-Yossef <gilad@benyossef.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Avi Kivity <avi@redhat.com>
Acked-by: default avatarMichal Nazarewicz <mina86@mina86.org>
Cc: Kosaki Motohiro <kosaki.motohiro@gmail.com>
Cc: Milton Miller <miltonm@bga.com>
Reviewed-by: default avatar"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3fc498f1

include/linux/smp.h

+24 −0
Original line number Diff line number Diff line
@@ -108,6 +108,15 @@ int on_each_cpu(smp_call_func_t func, void *info, int wait); 
void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,

		void *info, bool wait);



/*

 * Call a function on each processor for which the supplied function

 * cond_func returns a positive value. This may include the local

 * processor.

 */

void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),

		smp_call_func_t func, void *info, bool wait,

		gfp_t gfp_flags);



/*

 * Mark the boot cpu "online" so that it can call console drivers in

 * printk() and can access its per-cpu storage.
@@ -153,6 +162,21 @@ static inline int up_smp_call_function(smp_call_func_t func, void *info) 
			local_irq_enable();		\

		}					\

	} while (0)

/*

 * Preemption is disabled here to make sure the cond_func is called under the

 * same condtions in UP and SMP.

 */

#define on_each_cpu_cond(cond_func, func, info, wait, gfp_flags)\

	do {							\

		void *__info = (info);				\

		preempt_disable();				\

		if ((cond_func)(0, __info)) {			\

			local_irq_disable();			\

			(func)(__info);				\

			local_irq_enable();			\

		}						\

		preempt_enable();				\

	} while (0)



static inline void smp_send_reschedule(int cpu) { }

#define num_booting_cpus()			1

kernel/smp.c

+61 −0
Original line number Diff line number Diff line
@@ -730,3 +730,64 @@ void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, 
	put_cpu();

}

EXPORT_SYMBOL(on_each_cpu_mask);



/*

 * on_each_cpu_cond(): Call a function on each processor for which

 * the supplied function cond_func returns true, optionally waiting

 * for all the required CPUs to finish. This may include the local

 * processor.

 * @cond_func:	A callback function that is passed a cpu id and

 *		the the info parameter. The function is called

 *		with preemption disabled. The function should

 *		return a blooean value indicating whether to IPI

 *		the specified CPU.

 * @func:	The function to run on all applicable CPUs.

 *		This must be fast and non-blocking.

 * @info:	An arbitrary pointer to pass to both functions.

 * @wait:	If true, wait (atomically) until function has

 *		completed on other CPUs.

 * @gfp_flags:	GFP flags to use when allocating the cpumask

 *		used internally by the function.

 *

 * The function might sleep if the GFP flags indicates a non

 * atomic allocation is allowed.

 *

 * Preemption is disabled to protect against CPUs going offline but not online.

 * CPUs going online during the call will not be seen or sent an IPI.

 *

 * You must not call this function with disabled interrupts or

 * from a hardware interrupt handler or from a bottom half handler.

 */

void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),

			smp_call_func_t func, void *info, bool wait,

			gfp_t gfp_flags)

{

	cpumask_var_t cpus;

	int cpu, ret;



	might_sleep_if(gfp_flags & __GFP_WAIT);



	if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {

		preempt_disable();

		for_each_online_cpu(cpu)

			if (cond_func(cpu, info))

				cpumask_set_cpu(cpu, cpus);

		on_each_cpu_mask(cpus, func, info, wait);

		preempt_enable();

		free_cpumask_var(cpus);

	} else {

		/*

		 * No free cpumask, bother. No matter, we'll

		 * just have to IPI them one by one.

		 */

		preempt_disable();

		for_each_online_cpu(cpu)

			if (cond_func(cpu, info)) {

				ret = smp_call_function_single(cpu, func,

								info, wait);

				WARN_ON_ONCE(!ret);

			}

		preempt_enable();

	}

}

EXPORT_SYMBOL(on_each_cpu_cond);