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authorGilad Ben-Yossef <gilad@benyossef.com>2012-03-28 14:42:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-28 17:14:35 -0700
commitb3a7e98e024ffa9f7e4554dd720c508015c4a831 (patch)
tree50c09e1a47418ba4bb55b11f756bf4d99cf76123 /kernel/smp.c
parent3fc498f165304dc913f1d13b5ac9ab4c758ee7ab (diff)
downloadlwn-b3a7e98e024ffa9f7e4554dd720c508015c4a831.tar.gz
lwn-b3a7e98e024ffa9f7e4554dd720c508015c4a831.zip
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: Gilad Ben-Yossef <gilad@benyossef.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux-foundation.org> Acked-by: Peter 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: Michal Nazarewicz <mina86@mina86.org> Cc: Kosaki Motohiro <kosaki.motohiro@gmail.com> Cc: Milton Miller <miltonm@bga.com> Reviewed-by: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/smp.c')
-rw-r--r--kernel/smp.c61
1 files changed, 61 insertions, 0 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index a081e6ce0e0a..2f8b10ecf759 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -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);