From: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Introduce cpu_idle_wait() on architectures requiring modification of
pm_idle from modules, this will ensure that all processors have updated
their cached values of pm_idle upon exit. This patch is to address the bug
report at http://bugme.osdl.org/show_bug.cgi?id=1716 and replaces the
current code fix which is in violation of normal RCU usage as pointed out
by Stephen, Dipankar and Paul.
Signed-off-by: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/arch/i386/kernel/apm.c | 2 +-
25-akpm/arch/i386/kernel/process.c | 30 +++++++++++++++++++++++-------
25-akpm/arch/ia64/kernel/process.c | 30 +++++++++++++++++++++++-------
25-akpm/arch/x86_64/kernel/process.c | 31 ++++++++++++++++++++++++-------
25-akpm/drivers/acpi/processor.c | 2 +-
25-akpm/include/asm-i386/system.h | 1 +
25-akpm/include/asm-ia64/system.h | 1 +
25-akpm/include/asm-x86_64/system.h | 2 ++
8 files changed, 76 insertions(+), 23 deletions(-)
diff -puN arch/i386/kernel/apm.c~remove-rcu-abuse-in-cpu_idle arch/i386/kernel/apm.c
--- 25/arch/i386/kernel/apm.c~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.151927368 -0800
+++ 25-akpm/arch/i386/kernel/apm.c 2004-12-11 22:29:47.167924936 -0800
@@ -2369,7 +2369,7 @@ static void __exit apm_exit(void)
* (pm_idle), Wait for all processors to update cached/local
* copies of pm_idle before proceeding.
*/
- synchronize_kernel();
+ cpu_idle_wait();
}
if (((apm_info.bios.flags & APM_BIOS_DISENGAGED) == 0)
&& (apm_info.connection_version > 0x0100)) {
diff -puN arch/i386/kernel/process.c~remove-rcu-abuse-in-cpu_idle arch/i386/kernel/process.c
--- 25/arch/i386/kernel/process.c~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.153927064 -0800
+++ 25-akpm/arch/i386/kernel/process.c 2004-12-11 22:29:47.168924784 -0800
@@ -72,6 +72,7 @@ unsigned long thread_saved_pc(struct tas
* Powermanagement idle function, if any..
*/
void (*pm_idle)(void);
+static cpumask_t cpu_idle_map;
void disable_hlt(void)
{
@@ -144,16 +145,16 @@ static void poll_idle (void)
*/
void cpu_idle (void)
{
+ int cpu = smp_processor_id();
+
/* endless idle loop with no priority at all */
while (1) {
while (!need_resched()) {
void (*idle)(void);
- /*
- * Mark this as an RCU critical section so that
- * synchronize_kernel() in the unload path waits
- * for our completion.
- */
- rcu_read_lock();
+
+ if (cpu_isset(cpu, cpu_idle_map))
+ cpu_clear(cpu, cpu_idle_map);
+ rmb();
idle = pm_idle;
if (!idle)
@@ -161,12 +162,27 @@ void cpu_idle (void)
irq_stat[smp_processor_id()].idle_timestamp = jiffies;
idle();
- rcu_read_unlock();
}
schedule();
}
}
+void cpu_idle_wait(void)
+{
+ int cpu;
+ cpumask_t map;
+
+ for_each_online_cpu(cpu)
+ cpu_set(cpu, cpu_idle_map);
+
+ wmb();
+ do {
+ schedule_timeout(HZ);
+ cpus_and(map, cpu_idle_map, cpu_online_map);
+ } while (!cpus_empty(map));
+}
+EXPORT_SYMBOL_GPL(cpu_idle_wait);
+
/*
* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
* which can obviate IPI to trigger checking of need_resched.
diff -puN arch/ia64/kernel/process.c~remove-rcu-abuse-in-cpu_idle arch/ia64/kernel/process.c
--- 25/arch/ia64/kernel/process.c~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.154926912 -0800
+++ 25-akpm/arch/ia64/kernel/process.c 2004-12-11 22:29:47.169924632 -0800
@@ -46,6 +46,7 @@
#include "sigframe.h"
void (*ia64_mark_idle)(int);
+static cpumask_t cpu_idle_map;
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
@@ -225,10 +226,28 @@ static inline void play_dead(void)
}
#endif /* CONFIG_HOTPLUG_CPU */
+
+void cpu_idle_wait(void)
+{
+ int cpu;
+ cpumask_t map;
+
+ for_each_online_cpu(cpu)
+ cpu_set(cpu, cpu_idle_map);
+
+ wmb();
+ do {
+ schedule_timeout(HZ);
+ cpus_and(map, cpu_idle_map, cpu_online_map);
+ } while (!cpus_empty(map));
+}
+EXPORT_SYMBOL_GPL(cpu_idle_wait);
+
void __attribute__((noreturn))
cpu_idle (void *unused)
{
void (*mark_idle)(int) = ia64_mark_idle;
+ int cpu = smp_processor_id();
/* endless idle loop with no priority at all */
while (1) {
@@ -241,17 +260,14 @@ cpu_idle (void *unused)
if (mark_idle)
(*mark_idle)(1);
- /*
- * Mark this as an RCU critical section so that
- * synchronize_kernel() in the unload path waits
- * for our completion.
- */
- rcu_read_lock();
+
+ if (cpu_isset(cpu, cpu_idle_map))
+ cpu_clear(cpu, cpu_idle_map);
+ rmb();
idle = pm_idle;
if (!idle)
idle = default_idle;
(*idle)();
- rcu_read_unlock();
}
if (mark_idle)
diff -puN arch/x86_64/kernel/process.c~remove-rcu-abuse-in-cpu_idle arch/x86_64/kernel/process.c
--- 25/arch/x86_64/kernel/process.c~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.156926608 -0800
+++ 25-akpm/arch/x86_64/kernel/process.c 2004-12-11 22:29:47.170924480 -0800
@@ -61,6 +61,7 @@ EXPORT_SYMBOL(boot_option_idle_override)
* Powermanagement idle function, if any..
*/
void (*pm_idle)(void);
+static cpumask_t cpu_idle_map;
void disable_hlt(void)
{
@@ -123,6 +124,23 @@ static void poll_idle (void)
}
}
+
+void cpu_idle_wait(void)
+{
+ int cpu;
+ cpumask_t map;
+
+ for_each_online_cpu(cpu)
+ cpu_set(cpu, cpu_idle_map);
+
+ wmb();
+ do {
+ schedule_timeout(HZ);
+ cpus_and(map, cpu_idle_map, cpu_online_map);
+ } while (!cpus_empty(map));
+}
+EXPORT_SYMBOL_GPL(cpu_idle_wait);
+
/*
* The idle thread. There's no useful work to be
* done, so just try to conserve power and have a
@@ -131,21 +149,20 @@ static void poll_idle (void)
*/
void cpu_idle (void)
{
+ int cpu = smp_processor_id();
+
/* endless idle loop with no priority at all */
while (1) {
while (!need_resched()) {
void (*idle)(void);
- /*
- * Mark this as an RCU critical section so that
- * synchronize_kernel() in the unload path waits
- * for our completion.
- */
- rcu_read_lock();
+
+ if (cpu_isset(cpu, cpu_idle_map))
+ cpu_clear(cpu, cpu_idle_map);
+ rmb();
idle = pm_idle;
if (!idle)
idle = default_idle;
idle();
- rcu_read_unlock();
}
schedule();
}
diff -puN drivers/acpi/processor.c~remove-rcu-abuse-in-cpu_idle drivers/acpi/processor.c
--- 25/drivers/acpi/processor.c~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.158926304 -0800
+++ 25-akpm/drivers/acpi/processor.c 2004-12-11 22:29:47.172924176 -0800
@@ -2578,7 +2578,7 @@ acpi_processor_remove (
* (pm_idle), Wait for all processors to update cached/local
* copies of pm_idle before proceeding.
*/
- synchronize_kernel();
+ cpu_idle_wait();
}
status = acpi_remove_notify_handler(pr->handle, ACPI_DEVICE_NOTIFY,
diff -puN include/asm-i386/system.h~remove-rcu-abuse-in-cpu_idle include/asm-i386/system.h
--- 25/include/asm-i386/system.h~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.159926152 -0800
+++ 25-akpm/include/asm-i386/system.h 2004-12-11 22:29:47.173924024 -0800
@@ -543,5 +543,6 @@ void disable_hlt(void);
void enable_hlt(void);
extern int es7000_plat;
+void cpu_idle_wait(void);
#endif
diff -puN include/asm-ia64/system.h~remove-rcu-abuse-in-cpu_idle include/asm-ia64/system.h
--- 25/include/asm-ia64/system.h~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.160926000 -0800
+++ 25-akpm/include/asm-ia64/system.h 2004-12-11 22:29:47.173924024 -0800
@@ -284,6 +284,7 @@ do { \
#define ia64_platform_is(x) (strcmp(x, platform_name) == 0)
+void cpu_idle_wait(void);
#endif /* __KERNEL__ */
#endif /* __ASSEMBLY__ */
diff -puN include/asm-x86_64/system.h~remove-rcu-abuse-in-cpu_idle include/asm-x86_64/system.h
--- 25/include/asm-x86_64/system.h~remove-rcu-abuse-in-cpu_idle 2004-12-11 22:29:47.162925696 -0800
+++ 25-akpm/include/asm-x86_64/system.h 2004-12-11 22:29:47.174923872 -0800
@@ -326,6 +326,8 @@ static inline unsigned long __cmpxchg(vo
/* For spinlocks etc */
#define local_irq_save(x) do { warn_if_not_ulong(x); __asm__ __volatile__("# local_irq_save \n\t pushfq ; popq %0 ; cli":"=g" (x): /* no input */ :"memory"); } while (0)
+void cpu_idle_wait(void);
+
/*
* disable hlt during certain critical i/o operations
*/
_