From bf51935f3e988e0ed6f34b55593e5912f990750a Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 17 Feb 2009 06:01:30 -0800 Subject: x86, rcu: fix strange load average and ksoftirqd behavior Damien Wyart reported high ksoftirqd CPU usage (20%) on an otherwise idle system. The function-graph trace Damien provided: > 799.521187 | 1) -0 | | rcu_check_callbacks() { > 799.521371 | 1) -0 | | rcu_check_callbacks() { > 799.521555 | 1) -0 | | rcu_check_callbacks() { > 799.521738 | 1) -0 | | rcu_check_callbacks() { > 799.521934 | 1) -0 | | rcu_check_callbacks() { > 799.522068 | 1) ksoftir-2324 | | rcu_check_callbacks() { > 799.522208 | 1) -0 | | rcu_check_callbacks() { > 799.522392 | 1) -0 | | rcu_check_callbacks() { > 799.522575 | 1) -0 | | rcu_check_callbacks() { > 799.522759 | 1) -0 | | rcu_check_callbacks() { > 799.522956 | 1) -0 | | rcu_check_callbacks() { > 799.523074 | 1) ksoftir-2324 | | rcu_check_callbacks() { > 799.523214 | 1) -0 | | rcu_check_callbacks() { > 799.523397 | 1) -0 | | rcu_check_callbacks() { > 799.523579 | 1) -0 | | rcu_check_callbacks() { > 799.523762 | 1) -0 | | rcu_check_callbacks() { > 799.523960 | 1) -0 | | rcu_check_callbacks() { > 799.524079 | 1) ksoftir-2324 | | rcu_check_callbacks() { > 799.524220 | 1) -0 | | rcu_check_callbacks() { > 799.524403 | 1) -0 | | rcu_check_callbacks() { > 799.524587 | 1) -0 | | rcu_check_callbacks() { > 799.524770 | 1) -0 | | rcu_check_callbacks() { > [ . . . ] Shows rcu_check_callbacks() being invoked way too often. It should be called once per jiffy, and here it is called no less than 22 times in about 3.5 milliseconds, meaning one call every 160 microseconds or so. Why do we need to call rcu_pending() and rcu_check_callbacks() from the idle loop of 32-bit x86, especially given that no other architecture does this? The following patch removes the call to rcu_pending() and rcu_check_callbacks() from the x86 32-bit idle loop in order to reduce the softirq load on idle systems. Reported-by: Damien Wyart Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- arch/x86/kernel/process_32.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index a546f55c77b..bd4da2af08a 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -104,9 +104,6 @@ void cpu_idle(void) check_pgt_cache(); rmb(); - if (rcu_pending(cpu)) - rcu_check_callbacks(cpu, 0); - if (cpu_is_offline(cpu)) play_dead(); -- cgit v1.2.3 From 6ec68bff3c81e776a455f6aca95c8c5f1d630198 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 12 Feb 2009 13:39:26 +0100 Subject: x86, mce: reinitialize per cpu features on resume Impact: Bug fix This fixes a long standing bug in the machine check code. On resume the boot CPU wouldn't get its vendor specific state like thermal handling reinitialized. This means the boot cpu wouldn't ever get any thermal events reported again. Call the respective initialization functions on resume v2: Remove ancient init because they don't have a resume device anyways. Pointed out by Thomas Gleixner. v3: Now fix the Subject too to reflect v2 change Signed-off-by: Andi Kleen Acked-by: Thomas Gleixner Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/mcheck/mce_64.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/cpu/mcheck/mce_64.c b/arch/x86/kernel/cpu/mcheck/mce_64.c index 1c838032fd3..1f184efb6bc 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_64.c +++ b/arch/x86/kernel/cpu/mcheck/mce_64.c @@ -734,6 +734,7 @@ __setup("mce=", mcheck_enable); static int mce_resume(struct sys_device *dev) { mce_init(NULL); + mce_cpu_features(¤t_cpu_data); return 0; } -- cgit v1.2.3 From 380851bc6b1b4107c61dfa2997f9095dcf779336 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 12 Feb 2009 13:39:33 +0100 Subject: x86, mce: use force_sig_info to kill process in machine check Impact: bug fix (with tolerant == 3) do_exit cannot be called directly from the exception handler because it can sleep and the exception handler runs on the exception stack. Use force_sig() instead. Based on a earlier patch by Ying Huang who debugged the problem. Signed-off-by: Andi Kleen Acked-by: Thomas Gleixner Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/mcheck/mce_64.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce_64.c b/arch/x86/kernel/cpu/mcheck/mce_64.c index 1f184efb6bc..25cf624eccb 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_64.c +++ b/arch/x86/kernel/cpu/mcheck/mce_64.c @@ -295,11 +295,11 @@ void do_machine_check(struct pt_regs * regs, long error_code) * If we know that the error was in user space, send a * SIGBUS. Otherwise, panic if tolerance is low. * - * do_exit() takes an awful lot of locks and has a slight + * force_sig() takes an awful lot of locks and has a slight * risk of deadlocking. */ if (user_space) { - do_exit(SIGBUS); + force_sig(SIGBUS, current); } else if (panic_on_oops || tolerant < 2) { mce_panic("Uncorrected machine check", &panicm, mcestart); -- cgit v1.2.3 From 07db1c140eb233971341396e492cc73d4280e698 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 12 Feb 2009 13:39:35 +0100 Subject: x86, mce: fix ifdef for 64bit thermal apic vector clear on shutdown Impact: Bugfix The ifdef for the apic clear on shutdown for the 64bit intel thermal vector was incorrect and never triggered. Fix that. Signed-off-by: Andi Kleen Acked-by: Thomas Gleixner Signed-off-by: H. Peter Anvin --- arch/x86/kernel/apic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c index 115449f869e..570f36e44e5 100644 --- a/arch/x86/kernel/apic.c +++ b/arch/x86/kernel/apic.c @@ -862,7 +862,7 @@ void clear_local_APIC(void) } /* lets not touch this if we didn't frob it */ -#if defined(CONFIG_X86_MCE_P4THERMAL) || defined(X86_MCE_INTEL) +#if defined(CONFIG_X86_MCE_P4THERMAL) || defined(CONFIG_X86_MCE_INTEL) if (maxlvt >= 5) { v = apic_read(APIC_LVTTHMR); apic_write(APIC_LVTTHMR, v | APIC_LVT_MASKED); -- cgit v1.2.3