From 42eb088ed246a5a817bb45a8b32fe234cf1c0f8b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 19 Nov 2013 16:41:49 +0100 Subject: sched: Avoid NULL dereference on sd_busy Commit 37dc6b50cee9 ("sched: Remove unnecessary iteration over sched domains to update nr_busy_cpus") forgot to clear 'sd_busy' under some conditions leading to a possible NULL deref in set_cpu_sd_state_idle(). Reported-by: Anton Blanchard Cc: Preeti U Murthy Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20131118113701.GF3866@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c1808606ee5..a1591ca7eb5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4910,8 +4910,9 @@ static void update_top_cache_domain(int cpu) if (sd) { id = cpumask_first(sched_domain_span(sd)); size = cpumask_weight(sched_domain_span(sd)); - rcu_assign_pointer(per_cpu(sd_busy, cpu), sd->parent); + sd = sd->parent; /* sd_busy */ } + rcu_assign_pointer(per_cpu(sd_busy, cpu), sd); rcu_assign_pointer(per_cpu(sd_llc, cpu), sd); per_cpu(sd_llc_size, cpu) = size; -- cgit v1.2.3-70-g09d2 From 0515973ffb16c2852a1bb1df2ca1456556faaaa5 Mon Sep 17 00:00:00 2001 From: Shigeru Yoshida Date: Sun, 17 Nov 2013 12:12:36 +0900 Subject: sched: Fix a trivial typo in comments Fix a trivial typo in rq_attach_root(). Signed-off-by: Shigeru Yoshida Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20131117.121236.1990617639803941055.shigeru.yoshida@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a1591ca7eb5..718730dd048 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4762,7 +4762,7 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd) cpumask_clear_cpu(rq->cpu, old_rd->span); /* - * If we dont want to free the old_rt yet then + * If we dont want to free the old_rd yet then * set old_rd to NULL to skip the freeing later * in this function: */ -- cgit v1.2.3-70-g09d2 From 32e475d76a3e40879cd9ee4f69b19615062280d7 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 21 Nov 2013 12:41:44 +0100 Subject: sched: Expose preempt_schedule_irq() Tony reported that aa0d53260596 ("ia64: Use preempt_schedule_irq") broke PREEMPT=n builds on ia64. Ok, wrapped my brain around it. I tripped over the magic asm foo which has a single need_resched check and schedule point for both sys call return and interrupt return. So you need the schedule_preempt_irq() for kernel preemption from interrupt return while on a normal syscall preemption a schedule would be sufficient. But using schedule_preempt_irq() is not harmful here in any way. It just sets the preempt_active bit also in cases where it would not be required. Even on preempt=n kernels adding the preempt_active bit is completely harmless. So instead of having an extra function, moving the existing one out of the ifdef PREEMPT looks like the sanest thing to do. It would also allow getting rid of various other sti/schedule/cli asm magic in other archs. Reported-and-Tested-by: Tony Luck Fixes: aa0d53260596 ("ia64: Use preempt_schedule_irq") Signed-off-by: Thomas Gleixner [slightly edited Changelog] Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1311211230030.30673@ionos.tec.linutronix.de Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 718730dd048..e85cda20ab2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2660,6 +2660,7 @@ asmlinkage void __sched notrace preempt_schedule(void) } while (need_resched()); } EXPORT_SYMBOL(preempt_schedule); +#endif /* CONFIG_PREEMPT */ /* * this is the entry point to schedule() from kernel preemption @@ -2693,8 +2694,6 @@ asmlinkage void __sched preempt_schedule_irq(void) exception_exit(prev_state); } -#endif /* CONFIG_PREEMPT */ - int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags, void *key) { -- cgit v1.2.3-70-g09d2 From 8e8339a3a1069141985daaa2521ba304509ddecd Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 11 Dec 2013 11:09:53 +0100 Subject: sched: Initialize power_orig for overlapping groups Yinghai reported that he saw a /0 in sg_capacity on his EX parts. Make sure to always initialize power_orig now that we actually use it. Ideally build_sched_domains() -> init_sched_groups_power() would also initialize this; but for some yet unexplained reason some setups seem to miss updates there. Reported-by: Yinghai Lu Tested-by: Yinghai Lu Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-l8ng2m9uml6fhibln8wqpom7@git.kernel.org Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e85cda20ab2..19af58f3a26 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5112,6 +5112,7 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu) * die on a /0 trap. */ sg->sgp->power = SCHED_POWER_SCALE * cpumask_weight(sg_span); + sg->sgp->power_orig = sg->sgp->power; /* * Make sure the first group of this domain contains the -- cgit v1.2.3-70-g09d2 From 5d4cf996cf134e8ddb4f906b8197feb9267c2b77 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 17 Dec 2013 09:21:25 +0000 Subject: sched: Assign correct scheduling domain to 'sd_llc' Commit 42eb088e (sched: Avoid NULL dereference on sd_busy) corrected a NULL dereference on sd_busy but the fix also altered what scheduling domain it used for the 'sd_llc' percpu variable. One impact of this is that a task selecting a runqueue may consider idle CPUs that are not cache siblings as candidates for running. Tasks are then running on CPUs that are not cache hot. This was found through bisection where ebizzy threads were not seeing equal performance and it looked like a scheduling fairness issue. This patch mitigates but does not completely fix the problem on all machines tested implying there may be an additional bug or a common root cause. Here are the average range of performance seen by individual ebizzy threads. It was tested on top of candidate patches related to x86 TLB range flushing. 4-core machine 3.13.0-rc3 3.13.0-rc3 vanilla fixsd-v3r3 Mean 1 0.00 ( 0.00%) 0.00 ( 0.00%) Mean 2 0.34 ( 0.00%) 0.10 ( 70.59%) Mean 3 1.29 ( 0.00%) 0.93 ( 27.91%) Mean 4 7.08 ( 0.00%) 0.77 ( 89.12%) Mean 5 193.54 ( 0.00%) 2.14 ( 98.89%) Mean 6 151.12 ( 0.00%) 2.06 ( 98.64%) Mean 7 115.38 ( 0.00%) 2.04 ( 98.23%) Mean 8 108.65 ( 0.00%) 1.92 ( 98.23%) 8-core machine Mean 1 0.00 ( 0.00%) 0.00 ( 0.00%) Mean 2 0.40 ( 0.00%) 0.21 ( 47.50%) Mean 3 23.73 ( 0.00%) 0.89 ( 96.25%) Mean 4 12.79 ( 0.00%) 1.04 ( 91.87%) Mean 5 13.08 ( 0.00%) 2.42 ( 81.50%) Mean 6 23.21 ( 0.00%) 69.46 (-199.27%) Mean 7 15.85 ( 0.00%) 101.72 (-541.77%) Mean 8 109.37 ( 0.00%) 19.13 ( 82.51%) Mean 12 124.84 ( 0.00%) 28.62 ( 77.07%) Mean 16 113.50 ( 0.00%) 24.16 ( 78.71%) It's eliminated for one machine and reduced for another. Signed-off-by: Mel Gorman Signed-off-by: Peter Zijlstra Cc: Alex Shi Cc: Andrew Morton Cc: Fengguang Wu Cc: H Peter Anvin Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20131217092124.GV11295@suse.de Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 19af58f3a26..a88f4a485c5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4902,6 +4902,7 @@ DEFINE_PER_CPU(struct sched_domain *, sd_asym); static void update_top_cache_domain(int cpu) { struct sched_domain *sd; + struct sched_domain *busy_sd = NULL; int id = cpu; int size = 1; @@ -4909,9 +4910,9 @@ static void update_top_cache_domain(int cpu) if (sd) { id = cpumask_first(sched_domain_span(sd)); size = cpumask_weight(sched_domain_span(sd)); - sd = sd->parent; /* sd_busy */ + busy_sd = sd->parent; /* sd_busy */ } - rcu_assign_pointer(per_cpu(sd_busy, cpu), sd); + rcu_assign_pointer(per_cpu(sd_busy, cpu), busy_sd); rcu_assign_pointer(per_cpu(sd_llc, cpu), sd); per_cpu(sd_llc_size, cpu) = size; -- cgit v1.2.3-70-g09d2