[PATCH] Kick CPUS that might be sleeping in cpus_idle_wait

[Steven Rostedt]

This patch is different than the first patch I sent out.
This one just sends an IPI to all CPUS that don't check in after 1 sec.


Sometimes cpu_idle_wait gets stuck because it might miss CPUS that are
already in idle, have no tasks waiting to run and have no interrupts
going to them.  This is common on bootup when switching cpu idle
governors.

This patch gives those CPUS that don't check in an IPI kick.

Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
 arch/x86/kernel/process_32.c |   11 +++++++++++
 arch/x86/kernel/process_64.c |   11 +++++++++++
 2 files changed, 22 insertions(+)

Index: linux-compile-i386.git/arch/x86/kernel/process_32.c
===================================================================
--- linux-compile-i386.git.orig/arch/x86/kernel/process_32.c	2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/arch/x86/kernel/process_32.c	2008-01-09 14:09:45.000000000 -0500
@@ -204,6 +204,10 @@ void cpu_idle(void)
 	}
 }
 
+static void do_nothing(void *unused)
+{
+}
+
 void cpu_idle_wait(void)
 {
 	unsigned int cpu, this_cpu = get_cpu();
@@ -228,6 +232,13 @@ void cpu_idle_wait(void)
 				cpu_clear(cpu, map);
 		}
 		cpus_and(map, map, cpu_online_map);
+		/*
+		 * We waited 1 sec, if a CPU still did not call idle
+		 * it may be because it is in idle and not waking up
+		 * because it has nothing to do.
+		 * Give all the remaining CPUS a kick.
+		 */
+		smp_call_function_mask(map, do_nothing, 0, 0);
 	} while (!cpus_empty(map));
 
 	set_cpus_allowed(current, tmp);
Index: linux-compile-i386.git/arch/x86/kernel/process_64.c
===================================================================
--- linux-compile-i386.git.orig/arch/x86/kernel/process_64.c	2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/arch/x86/kernel/process_64.c	2008-01-09 15:17:20.000000000 -0500
@@ -135,6 +135,10 @@ static void poll_idle (void)
 	cpu_relax();
 }
 
+static void do_nothing(void *unused)
+{
+}
+
 void cpu_idle_wait(void)
 {
 	unsigned int cpu, this_cpu = get_cpu();
@@ -160,6 +164,13 @@ void cpu_idle_wait(void)
 				cpu_clear(cpu, map);
 		}
 		cpus_and(map, map, cpu_online_map);
+		/*
+		 * We waited 1 sec, if a CPU still did not call idle
+		 * it may be because it is in idle and not waking up
+		 * because it has nothing to do.
+		 * Give all the remaining CPUS a kick.
+		 */
+		smp_call_function_mask(map, do_nothing, 0, 0);
 	} while (!cpus_empty(map));
 
 	set_cpus_allowed(current, tmp);


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