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.
Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>
CC: Chris Metcalf <cmetcalf@xxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
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: Sasha Levin <levinsasha928@xxxxxxxxx>
CC: Rik van Riel <riel@xxxxxxxxxx>
CC: Andi Kleen <andi@xxxxxxxxxxxxxx>
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: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/smp.h | 16 ++++++++++++++++
kernel/smp.c | 38 ++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+), 0 deletions(-)
diff --git a/include/linux/smp.h b/include/linux/smp.h
index a3a14d9..a37f388 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -109,6 +109,14 @@ void on_each_cpu_mask(const struct cpumask *mask, void (*func)(void *),
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(int (*cond_func) (int cpu, void *info),
+ void (*func)(void *), 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.
*/
@@ -153,6 +161,14 @@ static inline int up_smp_call_function(smp_call_func_t func, void *info)
local_irq_enable(); \
} \
} while (0)
+#define on_each_cpu_cond(cond_func, func, info, wait) \
+ do { \
+ if (cond_func(0, info)) { \
+ local_irq_disable(); \
+ (func)(info); \
+ local_irq_enable(); \
+ } \
+ } while (0)
static inline void smp_send_reschedule(int cpu) { }
#define num_booting_cpus() 1
diff --git a/kernel/smp.c b/kernel/smp.c
index 7c0cbd7..bd8f4ad 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -721,3 +721,41 @@ void on_each_cpu_mask(const struct cpumask *mask, void (*func)(void *),
put_cpu();
}
EXPORT_SYMBOL(on_each_cpu_mask);
+
+/*
+ * Call a function on each processor for which the supplied function
+ * cond_func returns a positive value. This may include the local
+ * processor, optionally waiting for all the required CPUs to finish.
+ * All the limitations specified in smp_call_function_many apply.
+ */
+void on_each_cpu_cond(int (*cond_func) (int cpu, void *info),
+ void (*func)(void *), void *info, bool wait)
+{
+ cpumask_var_t cpus;
+ int cpu;
+
+ if (likely(zalloc_cpumask_var(&cpus, GFP_ATOMIC))) {
+ for_each_online_cpu(cpu)
+ if (cond_func(cpu, info))
+ cpumask_set_cpu(cpu, cpus);
+ on_each_cpu_mask(cpus, func, info, wait);
+ free_cpumask_var(cpus);
+ } else {
+ /*
+ * No free cpumask, bother. No matter, we'll
+ * just have to IPI them one by one.
+ */
+ for_each_online_cpu(cpu)
+ if (cond_func(cpu, info))
+ /*
+ * This call can fail if we ask it to IPI an
+ * offline CPU, but this can be a valid
+ * sceanrio here. Also, on_each_cpu_mask
+ * ignores offlines CPUs. So, we ignore
+ * the return value here.
+ */
+ smp_call_function_single(cpu, func, info, wait);
+ }
+}
+EXPORT_SYMBOL(on_each_cpu_cond);
+
--
1.7.0.4
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