Messages in this thread Patch in this message | | | Date | Sat, 11 Dec 2004 21:54:42 -0700 (MST) | From | Zwane Mwaikambo <> | Subject | [PATCH] Remove RCU abuse in cpu_idle() |
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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.
Tested on EM64T/SMP/x86_64 with modprobe/rmmod loops of ACPI processor/thermal modules.
arch/i386/kernel/apm.c | 2 +- arch/i386/kernel/process.c | 27 ++++++++++++++++++++------- arch/ia64/kernel/process.c | 26 +++++++++++++++++++------- arch/x86_64/kernel/process.c | 27 ++++++++++++++++++++------- drivers/acpi/processor.c | 2 +- include/asm-i386/system.h | 1 + include/asm-ia64/system.h | 1 + include/asm-x86_64/system.h | 2 ++ 8 files changed, 65 insertions(+), 23 deletions(-)
Signed-off-by: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Index: linux-2.6.10-rc2/arch/i386/kernel/apm.c =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/arch/i386/kernel/apm.c,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 apm.c --- linux-2.6.10-rc2/arch/i386/kernel/apm.c 25 Nov 2004 19:45:32 -0000 1.1.1.1 +++ linux-2.6.10-rc2/arch/i386/kernel/apm.c 12 Dec 2004 04:28:11 -0000 @@ -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)) { Index: linux-2.6.10-rc2/arch/i386/kernel/process.c =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/arch/i386/kernel/process.c,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 process.c --- linux-2.6.10-rc2/arch/i386/kernel/process.c 25 Nov 2004 19:45:32 -0000 1.1.1.1 +++ linux-2.6.10-rc2/arch/i386/kernel/process.c 12 Dec 2004 04:29:51 -0000 @@ -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) { @@ -142,16 +143,16 @@ 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) @@ -159,12 +160,24 @@ void cpu_idle (void) irq_stat[smp_processor_id()].idle_timestamp = jiffies; idle(); - rcu_read_unlock(); } schedule(); } } +void cpu_idle_wait(void) +{ + int cpu; + + for_each_online_cpu(cpu) + cpu_set(cpu, cpu_idle_map); + + wmb(); + while (cpus_equal(cpu_idle_map, cpu_online_map)) + schedule_timeout(HZ); +} +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. Index: linux-2.6.10-rc2/arch/ia64/kernel/process.c =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/arch/ia64/kernel/process.c,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 process.c --- linux-2.6.10-rc2/arch/ia64/kernel/process.c 25 Nov 2004 19:45:32 -0000 1.1.1.1 +++ linux-2.6.10-rc2/arch/ia64/kernel/process.c 12 Dec 2004 04:28:11 -0000 @@ -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); @@ -223,10 +224,24 @@ static inline void play_dead(void) } #endif /* CONFIG_HOTPLUG_CPU */ +void cpu_idle_wait(void) +{ + int cpu; + + for_each_online_cpu(cpu) + cpu_set(cpu, cpu_idle_map); + + wmb(); + while (cpus_equal(cpu_idle_map, cpu_online_map)) + schedule_timeout(HZ); +} +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) { @@ -239,17 +254,14 @@ 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) Index: linux-2.6.10-rc2/arch/x86_64/kernel/process.c =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/arch/x86_64/kernel/process.c,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 process.c --- linux-2.6.10-rc2/arch/x86_64/kernel/process.c 25 Nov 2004 19:45:32 -0000 1.1.1.1 +++ linux-2.6.10-rc2/arch/x86_64/kernel/process.c 12 Dec 2004 04:28:11 -0000 @@ -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 +124,19 @@ static void poll_idle (void) } } +void cpu_idle_wait(void) +{ + int cpu; + + for_each_online_cpu(cpu) + cpu_set(cpu, cpu_idle_map); + + wmb(); + while (cpus_equal(cpu_idle_map, cpu_online_map)) + schedule_timeout(HZ); +} +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 +145,20 @@ 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(); } Index: linux-2.6.10-rc2/drivers/acpi/processor.c =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/drivers/acpi/processor.c,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 processor.c --- linux-2.6.10-rc2/drivers/acpi/processor.c 25 Nov 2004 19:45:34 -0000 1.1.1.1 +++ linux-2.6.10-rc2/drivers/acpi/processor.c 12 Dec 2004 04:28:11 -0000 @@ -2535,7 +2535,7 @@ 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, Index: linux-2.6.10-rc2/include/asm-i386/system.h =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/include/asm-i386/system.h,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 system.h --- linux-2.6.10-rc2/include/asm-i386/system.h 25 Nov 2004 19:45:33 -0000 1.1.1.1 +++ linux-2.6.10-rc2/include/asm-i386/system.h 12 Dec 2004 04:28:11 -0000 @@ -466,5 +466,6 @@ void disable_hlt(void); void enable_hlt(void); extern int es7000_plat; +void cpu_idle_wait(void); #endif Index: linux-2.6.10-rc2/include/asm-ia64/system.h =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/include/asm-ia64/system.h,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 system.h --- linux-2.6.10-rc2/include/asm-ia64/system.h 25 Nov 2004 19:45:33 -0000 1.1.1.1 +++ linux-2.6.10-rc2/include/asm-ia64/system.h 12 Dec 2004 04:28:11 -0000 @@ -284,6 +284,7 @@ do { \ #define ia64_platform_is(x) (strcmp(x, platform_name) == 0) +void cpu_idle_wait(void); #endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ Index: linux-2.6.10-rc2/include/asm-x86_64/system.h =================================================================== RCS file: /home/cvsroot/linux-2.6.10-rc2/include/asm-x86_64/system.h,v retrieving revision 1.1.1.1 diff -u -p -B -r1.1.1.1 system.h --- linux-2.6.10-rc2/include/asm-x86_64/system.h 25 Nov 2004 19:45:33 -0000 1.1.1.1 +++ linux-2.6.10-rc2/include/asm-x86_64/system.h 12 Dec 2004 04:28:11 -0000 @@ -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 */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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