linux/kernel/sched, branch v3.4

sched: Fix KVM and ia64 boot crash due to sched_groups circular linked list assumption

2012-05-09T10:27:35Z

If we have one cpu that failed to boot and boot cpu gave up on waiting for it and then another cpu is being booted, kernel might crash with following OOPS: BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 IP: [] __bitmap_weight+0x30/0x80 Call Trace: [] build_sched_domains+0x7b6/0xa50 The crash happens in init_sched_groups_power() that expects sched_groups to be circular linked list. However it is not always true, since sched_groups preallocated in __sdt_alloc are initialized in build_sched_groups and it may exit early if (cpu != cpumask_first(sched_domain_span(sd))) return 0; without initializing sd->groups->next field. Fix bug by initializing next field right after sched_group was allocated. Also-Reported-by: Jiang Liu Signed-off-by: Igor Mammedov Cc: a.p.zijlstra@chello.nl Cc: pjt@google.com Cc: seto.hidetoshi@jp.fujitsu.com Link: http://lkml.kernel.org/r/1336559908-32533-1-git-send-email-imammedo@redhat.com Signed-off-by: Ingo Molnar

sched: Fix OOPS when build_sched_domains() percpu allocation fails

2012-04-26T10:54:53Z

Under extreme memory used up situations, percpu allocation might fail. We hit it when system goes to suspend-to-ram, causing a kworker panic: EIP: [] build_sched_domains+0x23a/0xad0 Kernel panic - not syncing: Fatal exception Pid: 3026, comm: kworker/u:3 3.0.8-137473-gf42fbef #1 Call Trace: [] panic+0x66/0x16c [...] [] partition_sched_domains+0x287/0x4b0 [] cpuset_update_active_cpus+0x1fe/0x210 [] cpuset_cpu_inactive+0x1d/0x30 [...] With this fix applied build_sched_domains() will return -ENOMEM and the suspend attempt fails. Signed-off-by: he, bo Reviewed-by: Zhang, Yanmin Reviewed-by: Srivatsa S. Bhat Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Cc: Andrew Morton Cc: Link: http://lkml.kernel.org/r/1335355161.5892.17.camel@hebo [ So, we fail to deallocate a CPU because we cannot allocate RAM :-/ I don't like that kind of sad behavior but nevertheless it should not crash under high memory load. ] Signed-off-by: Ingo Molnar

sched: Fix more load-balancing fallout

2012-04-26T10:54:52Z

Commits 367456c756a6 ("sched: Ditch per cgroup task lists for load-balancing") and 5d6523ebd ("sched: Fix load-balance wreckage") left some more wreckage. By setting loop_max unconditionally to ->nr_running load-balancing could take a lot of time on very long runqueues (hackbench!). So keep the sysctl as max limit of the amount of tasks we'll iterate. Furthermore, the min load filter for migration completely fails with cgroups since inequality in per-cpu state can easily lead to such small loads :/ Furthermore the change to add new tasks to the tail of the queue instead of the head seems to have some effect.. not quite sure I understand why. Combined these fixes solve the huge hackbench regression reported by Tim when hackbench is ran in a cgroup. Reported-by: Tim Chen Acked-by: Tim Chen Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/r/1335365763.28150.267.camel@twins [ got rid of the CONFIG_PREEMPT tuning and made small readability edits ] Signed-off-by: Ingo Molnar

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-03-31T20:35:31Z

Pull scheduler fixes from Ingo Molnar. * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched: Fix incorrect usage of for_each_cpu_mask() in select_fallback_rq() sched: Fix __schedule_bug() output when called from an interrupt sched/arch: Introduce the finish_arch_post_lock_switch() scheduler callback

sched: Fix incorrect usage of for_each_cpu_mask() in select_fallback_rq()

2012-03-31T08:43:36Z

The function for_each_cpu_mask() expects a *pointer* to struct cpumask as its second argument, whereas select_fallback_rq() passes the value itself. And moreover, for_each_cpu_mask() has been marked as obselete in include/linux/cpumask.h. So move to the more appropriate for_each_cpu() variant. Reported-by: Sasha Levin Signed-off-by: Srivatsa S. Bhat Acked-by: Peter Zijlstra Cc: Dave Jones Cc: Liu Chuansheng Cc: vapier@gentoo.org Cc: rusty@rustcorp.com.au Link: http://lkml.kernel.org/r/4F75BED4.9050005@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2012-03-29T21:46:05Z

Pull scheduler fixes from Ingo Molnar. * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: cpusets: Remove an unused variable sched/rt: Improve pick_next_highest_task_rt() sched: Fix select_fallback_rq() vs cpu_active/cpu_online sched/x86/smp: Do not enable IRQs over calibrate_delay() sched: Fix compiler warning about declared inline after use MAINTAINERS: Update email address for SCHEDULER and PERF EVENTS

Merge branch 'sched/arch' into sched/urgent

2012-03-29T10:48:22Z

Merge reason: It has not gone upstream via the ARM tree, merge it via the scheduler tree. Signed-off-by: Ingo Molnar

sched: Fix __schedule_bug() output when called from an interrupt

2012-03-29T06:34:45Z

If schedule is called from an interrupt handler __schedule_bug() will call show_regs() with the registers saved during the interrupt handling done in do_IRQ(). This means we'll see the registers and the backtrace for the process that was interrupted and not the full backtrace explaining who called schedule(). This is due to 838225b ("sched: use show_regs() to improve __schedule_bug() output", 2007-10-24) which improperly assumed that get_irq_regs() would return the registers for the current stack because it is being called from within an interrupt handler. Simply remove the show_reg() code so that we dump a backtrace for the interrupt handler that called schedule(). [ I ran across this when I was presented with a scheduling while atomic log with a stacktrace pointing at spin_unlock_irqrestore(). It made no sense and I had to guess what interrupt handler could be called and poke around for someone calling schedule() in an interrupt handler. A simple test of putting an msleep() in an interrupt handler works better with this patch because you can actually see the msleep() call in the backtrace. ] Also-reported-by: Chris Metcalf Signed-off-by: Stephen Boyd Cc: Satyam Sharma Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1332979847-27102-1-git-send-email-sboyd@codeaurora.org Signed-off-by: Ingo Molnar

Add #includes needed to permit the removal of asm/system.h

2012-03-28T17:30:03Z

asm/system.h is a cause of circular dependency problems because it contains commonly used primitive stuff like barrier definitions and uncommonly used stuff like switch_to() that might require MMU definitions. asm/system.h has been disintegrated by this point on all arches into the following common segments: (1) asm/barrier.h Moved memory barrier definitions here. (2) asm/cmpxchg.h Moved xchg() and cmpxchg() here. #included in asm/atomic.h. (3) asm/bug.h Moved die() and similar here. (4) asm/exec.h Moved arch_align_stack() here. (5) asm/elf.h Moved AT_VECTOR_SIZE_ARCH here. (6) asm/switch_to.h Moved switch_to() here. Signed-off-by: David Howells

sched/rt: Improve pick_next_highest_task_rt()

2012-03-27T12:52:12Z

Avoid extra work by continuing on to the next rt_rq if the highest prio task in current rt_rq is the same priority as our candidate task. More detailed explanation: if next is not NULL, then we have found a candidate task, and its priority is next->prio. Now we are looking for an even higher priority task in the other rt_rq's. idx is the highest priority in the current candidate rt_rq. In the current 3.3 code, if idx is equal to next->prio, we would start scanning the tasks in that rt_rq and replace the current candidate task with a task from that rt_rq. But the new task would only have a priority that is equal to our previous candidate task, so we have not advanced our goal of finding a higher prio task. So we should avoid the extra work by continuing on to the next rt_rq if idx is equal to next->prio. Signed-off-by: Michael J Wang Acked-by: Steven Rostedt Reviewed-by: Yong Zhang Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/2EF88150C0EF2C43A218742ED384C1BC0FC83D6B@IRVEXCHMB08.corp.ad.broadcom.com Signed-off-by: Ingo Molnar