[PATCH v8 1/8] smp: introduce a generic on_each_cpu_mask function

[Gilad Ben-Yossef]

on_each_cpu_mask calls a function on processors specified by
cpumask, which may or may not include the local processor.

You must not call this function with disabled interrupts or
from a hardware interrupt handler or from a bottom half handler.

Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Reviewed-by: Christoph Lameter <cl@xxxxxxxxx>
CC: Chris Metcalf <cmetcalf@xxxxxxxxxx>
CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CC: Russell King <linux@xxxxxxxxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
CC: Pekka Enberg <penberg@xxxxxxxxxx>
CC: Matt Mackall <mpm@xxxxxxxxxxx>
CC: Rik van Riel <riel@xxxxxxxxxx>
CC: Andi Kleen <andi@xxxxxxxxxxxxxx>
CC: Sasha Levin <levinsasha928@xxxxxxxxx>
CC: Mel Gorman <mel@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: linux-fsdevel@xxxxxxxxxxxxxxx
CC: Avi Kivity <avi@xxxxxxxxxx>
CC: Michal Nazarewicz <mina86@xxxxxxxxxx>
CC: Kosaki Motohiro <kosaki.motohiro@xxxxxxxxx>
CC: Milton Miller <miltonm@xxxxxxx>
---
 include/linux/smp.h |   22 ++++++++++++++++++++++
 kernel/smp.c        |   29 +++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 0 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 8cc38d3..d0adb78 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -102,6 +102,13 @@ static inline void call_function_init(void) { }
 int on_each_cpu(smp_call_func_t func, void *info, int wait);
 
 /*
+ * Call a function on processors specified by mask, which might include
+ * the local one.
+ */
+void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
+		void *info, bool wait);
+
+/*
  * Mark the boot cpu "online" so that it can call console drivers in
  * printk() and can access its per-cpu storage.
  */
@@ -132,6 +139,21 @@ static inline int up_smp_call_function(smp_call_func_t func, void *info)
 		local_irq_enable();		\
 		0;				\
 	})
+/*
+ * Note we still need to test the mask even for UP
+ * because we actually can get an empty mask from
+ * code that on SMP might call us without the local
+ * CPU in the mask.
+ */
+#define on_each_cpu_mask(mask, func, info, wait) \
+	do {						\
+		if (cpumask_test_cpu(0, (mask))) {	\
+			local_irq_disable();		\
+			(func)(info);			\
+			local_irq_enable();		\
+		}					\
+	} while (0)
+
 static inline void smp_send_reschedule(int cpu) { }
 #define num_booting_cpus()			1
 #define smp_prepare_boot_cpu()			do {} while (0)
diff --git a/kernel/smp.c b/kernel/smp.c
index db197d6..a081e6c 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -701,3 +701,32 @@ int on_each_cpu(void (*func) (void *info), void *info, int wait)
 	return ret;
 }
 EXPORT_SYMBOL(on_each_cpu);
+
+/**
+ * on_each_cpu_mask(): Run a function on processors specified by
+ * cpumask, which may include the local processor.
+ * @mask: The set of cpus to run on (only runs on online subset).
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed
+ *        on other CPUs.
+ *
+ * If @wait is true, then returns once @func has returned.
+ *
+ * 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_mask(const struct cpumask *mask, smp_call_func_t func,
+			void *info, bool wait)
+{
+	int cpu = get_cpu();
+
+	smp_call_function_many(mask, func, info, wait);
+	if (cpumask_test_cpu(cpu, mask)) {
+		local_irq_disable();
+		func(info);
+		local_irq_enable();
+	}
+	put_cpu();
+}
+EXPORT_SYMBOL(on_each_cpu_mask);
-- 
1.7.0.4

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