[PATCH 17/20] SMP: Implement on_cpu()

Avi Kivity
2007-07-08T11:54:46Z

This defines on_cpu() which is similar to smp_call_function_single()
except that it works if cpu happens to be the current cpu. Can also be
seen as a complement to on_each_cpu() (which also doesn't treat the
current cpu specially).

Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
include/linux/smp.h | 16 ++++++++++++++++
kernel/softirq.c | 24 ++++++++++++++++++++++++
2 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 96ac21f..613edd2 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -7,6 +7,7 @@
*/

#include <linux/errno.h>
+#include <asm/system.h>

extern void cpu_idle(void);

@@ -61,6 +62,11 @@ int smp_call_function_single(int cpuid, void (*func) (void *info), void *info,
* Call a function on all processors
*/
int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait);
+/*
+ * Call a function on one processor
+ */
+int on_cpu(int cpu, void (*func)(void *info), void *info,
+ int retry, int wait);

#define MSG_ALL_BUT_SELF 0x8000 /* Assume <32768 CPU's */
#define MSG_ALL 0x8001
@@ -96,6 +102,16 @@ static inline int up_smp_call_function(void)
local_irq_enable(); \
0; \
})
+
+static inline int on_cpu(int cpu, void (*func)(void *info), void *info,
+ int retry, int wait)
+{
+ local_irq_disable();
+ func(info);
+ local_irq_enable();
+ return 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/softirq.c b/kernel/softirq.c
index 0b9886a..11666f7 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -658,4 +658,28 @@ int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait)
return ret;
}
EXPORT_SYMBOL(on_each_cpu);
+
+/*
+ * Call a function on one processor, which might be the currently executing
+ * processor.
+ */
+int on_cpu(int cpu, void (*func) (void *info), void *info,
+ int retry, int wait)
+{
+ int ret;
+ int this_cpu;
+
+ this_cpu = get_cpu();
+ if (this_cpu == cpu) {
+ local_irq_disable();
+ func(info);
+ local_irq_enable();
+ ret = 0;
+ } else
+ ret = smp_call_function_single(cpu, func, info, retry, wait);
+ put_cpu();
+ return ret;
+}
+EXPORT_SYMBOL(on_cpu);
+
#endif