linux/kernel/sched/core.c, branch v3.19

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

2015-02-06T21:34:26Z

Pull scheduler fixes from Ingo Molnar: "Misc fixes" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/deadline: Fix deadline parameter modification handling sched/wait: Remove might_sleep() from wait_event_cmd() sched: Fix crash if cpuset_cpumask_can_shrink() is passed an empty cpumask sched/fair: Avoid using uninitialized variable in preferred_group_nid()

sched/deadline: Fix deadline parameter modification handling

2015-02-04T06:42:48Z

Commit 67dfa1b756f2 ("sched/deadline: Implement cancel_dl_timer() to use in switched_from_dl()") removed the hrtimer_try_cancel() function call out from init_dl_task_timer(), which gets called from __setparam_dl(). The result is that we can now re-init the timer while its active -- this is bad and corrupts timer state. Furthermore; changing the parameters of an active deadline task is tricky in that you want to maintain guarantees, while immediately effective change would allow one to circumvent the CBS guarantees -- this too is bad, as one (bad) task should not be able to affect the others. Rework things to avoid both problems. We only need to initialize the timer once, so move that to __sched_fork() for new tasks. Then make sure __setparam_dl() doesn't affect the current running state but only updates the parameters used to calculate the next scheduling period -- this guarantees the CBS functions as expected (albeit slightly pessimistic). This however means we need to make sure __dl_clear_params() needs to reset the active state otherwise new (and tasks flipping between classes) will not properly (re)compute their first instance. Todo: close class flipping CBS hole. Todo: implement delayed BW release. Reported-by: Luca Abeni Acked-by: Juri Lelli Tested-by: Luca Abeni Fixes: 67dfa1b756f2 ("sched/deadline: Implement cancel_dl_timer() to use in switched_from_dl()") Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Kirill Tkhai Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20150128140803.GF23038@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar

sched: don't cause task state changes in nested sleep debugging

2015-02-01T20:23:32Z

Commit 8eb23b9f35aa ("sched: Debug nested sleeps") added code to report on nested sleep conditions, which we generally want to avoid because the inner sleeping operation can re-set the thread state to TASK_RUNNING, but that will then cause the outer sleep loop not actually sleep when it calls schedule. However, that's actually valid traditional behavior, with the inner sleep being some fairly rare case (like taking a sleeping lock that normally doesn't actually need to sleep). And the debug code would actually change the state of the task to TASK_RUNNING internally, which makes that kind of traditional and working code not work at all, because now the nested sleep doesn't just sometimes cause the outer one to not block, but will cause it to happen every time. In particular, it will cause the cardbus kernel daemon (pccardd) to basically busy-loop doing scheduling, converting a laptop into a heater, as reported by Bruno Prémont. But there may be other legacy uses of that nested sleep model in other drivers that are also likely to never get converted to the new model. This fixes both cases: - don't set TASK_RUNNING when the nested condition happens (note: even if WARN_ONCE() only _warns_ once, the return value isn't whether the warning happened, but whether the condition for the warning was true. So despite the warning only happening once, the "if (WARN_ON(..))" would trigger for every nested sleep. - in the cases where we knowingly disable the warning by using "sched_annotate_sleep()", don't change the task state (that is used for all core scheduling decisions), instead use '->task_state_change' that is used for the debugging decision itself. (Credit for the second part of the fix goes to Oleg Nesterov: "Can't we avoid this subtle change in behaviour DEBUG_ATOMIC_SLEEP adds?" with the suggested change to use 'task_state_change' as part of the test) Reported-and-bisected-by: Bruno Prémont Tested-by: Rafael J Wysocki Acked-by: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner , Cc: Ilya Dryomov , Cc: Mike Galbraith Cc: Ingo Molnar Cc: Peter Hurley , Cc: Davidlohr Bueso , Signed-off-by: Linus Torvalds

sched: Fix crash if cpuset_cpumask_can_shrink() is passed an empty cpumask

2015-01-28T14:28:15Z

While creating an exclusive cpuset, we passed cpuset_cpumask_can_shrink() an empty cpumask (cur), and dl_bw_of(cpumask_any(cur)) made boom with it: CPU: 0 PID: 6942 Comm: shield.sh Not tainted 3.19.0-master #19 Hardware name: MEDIONPC MS-7502/MS-7502, BIOS 6.00 PG 12/26/2007 task: ffff880224552450 ti: ffff8800caab8000 task.ti: ffff8800caab8000 RIP: 0010:[] [] cpuset_cpumask_can_shrink+0x56/0xb0 [...] Call Trace: [] validate_change+0x18a/0x200 [] cpuset_write_resmask+0x3b7/0x720 [] cgroup_file_write+0x38/0x100 [] kernfs_fop_write+0x12a/0x180 [] vfs_write+0xb3/0x1d0 [] SyS_write+0x46/0xb0 [] system_call_fastpath+0x16/0x1b Signed-off-by: Mike Galbraith Acked-by: Zefan Li Fixes: f82f80426f7a ("sched/deadline: Ensure that updates to exclusive cpusets don't break AC") Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1422417235.5716.5.camel@marge.simpson.net Signed-off-by: Ingo Molnar

sched: Fix KMALLOC_MAX_SIZE overflow during cpumask allocation

2014-12-23T10:43:48Z

When allocating space for load_balance_mask, in sched_init, when CPUMASK_OFFSTACK is set, we've managed to spill over KMALLOC_MAX_SIZE on our 6144 core machine. The patch below breaks up the allocations so that they don't overflow the max alloc size. It also allocates the masks on the the node from which they'll most commonly be accessed, to minimize remote accesses on NUMA machines. Suggested-by: George Beshers Signed-off-by: Alex Thorlton Cc: George Beshers Cc: Russ Anderson Cc: Peter Zijlstra Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1418928270-148543-1-git-send-email-athorlton@sgi.com Signed-off-by: Ingo Molnar

sched_show_task: fix unsafe usage of ->real_parent

2014-12-11T01:41:09Z

rcu_read_lock() can not protect p->real_parent if release_task(p) was already called, change sched_show_task() to check pis_alive() like other users do. Note: we need some helpers to cleanup the code like this. And it seems that that the usage of cpu_curr(cpu) in dump_cpu_task() is not safe too. Signed-off-by: Oleg Nesterov Cc: Aaron Tomlin Cc: Alexey Dobriyan Cc: "Eric W. Biederman" , Cc: Sterling Alexander Acked-by: Peter Zijlstra (Intel) Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

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

2014-12-10T05:21:34Z

Pull scheduler updates from Ingo Molnar: "The main changes in this cycle are: - 'Nested Sleep Debugging', activated when CONFIG_DEBUG_ATOMIC_SLEEP=y. This instruments might_sleep() checks to catch places that nest blocking primitives - such as mutex usage in a wait loop. Such bugs can result in hard to debug races/hangs. Another category of invalid nesting that this facility will detect is the calling of blocking functions from within schedule() -> sched_submit_work() -> blk_schedule_flush_plug(). There's some potential for false positives (if secondary blocking primitives themselves are not ready yet for this facility), but the kernel will warn once about such bugs per bootup, so the warning isn't much of a nuisance. This feature comes with a number of fixes, for problems uncovered with it, so no messages are expected normally. - Another round of sched/numa optimizations and refinements, for CONFIG_NUMA_BALANCING=y. - Another round of sched/dl fixes and refinements. Plus various smaller fixes and cleanups" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits) sched: Add missing rcu protection to wake_up_all_idle_cpus sched/deadline: Introduce start_hrtick_dl() for !CONFIG_SCHED_HRTICK sched/numa: Init numa balancing fields of init_task sched/deadline: Remove unnecessary definitions in cpudeadline.h sched/cpupri: Remove unnecessary definitions in cpupri.h sched/deadline: Fix rq->dl.pushable_tasks bug in push_dl_task() sched/fair: Fix stale overloaded status in the busiest group finding logic sched: Move p->nr_cpus_allowed check to select_task_rq() sched/completion: Document when to use wait_for_completion_io_*() sched: Update comments about CLONE_NEWUTS and CLONE_NEWIPC sched/fair: Kill task_struct::numa_entry and numa_group::task_list sched: Refactor task_struct to use numa_faults instead of numa_* pointers sched/deadline: Don't check CONFIG_SMP in switched_from_dl() sched/deadline: Reschedule from switched_from_dl() after a successful pull sched/deadline: Push task away if the deadline is equal to curr during wakeup sched/deadline: Add deadline rq status print sched/deadline: Fix artificial overrun introduced by yield_task_dl() sched/rt: Clean up check_preempt_equal_prio() sched/core: Use dl_bw_of() under rcu_read_lock_sched() sched: Check if we got a shallowest_idle_cpu before searching for least_loaded_cpu ...

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

2014-12-10T04:23:19Z

Pull RCU updates from Ingo Molnar: "These are the main changes in this cycle: - Streamline RCU's use of per-CPU variables, shifting from "cpu" arguments to functions to "this_"-style per-CPU variable accessors. - signal-handling RCU updates. - real-time updates. - torture-test updates. - miscellaneous fixes. - documentation updates" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits) rcu: Fix FIXME in rcu_tasks_kthread() rcu: More info about potential deadlocks with rcu_read_unlock() rcu: Optimize cond_resched_rcu_qs() rcu: Add sparse check for RCU_INIT_POINTER() documentation: memory-barriers.txt: Correct example for reorderings documentation: Add atomic_long_t to atomic_ops.txt documentation: Additional restriction for control dependencies documentation: Document RCU self test boot params rcutorture: Fix rcu_torture_cbflood() memory leak rcutorture: Remove obsolete kversion param in kvm.sh rcutorture: Remove stale test configurations rcutorture: Enable RCU self test in configs rcutorture: Add early boot self tests torture: Run Linux-kernel binary out of results directory cpu: Avoid puts_pending overflow rcu: Remove "cpu" argument to rcu_cleanup_after_idle() rcu: Remove "cpu" argument to rcu_prepare_for_idle() rcu: Remove "cpu" argument to rcu_needs_cpu() rcu: Remove "cpu" argument to rcu_note_context_switch() rcu: Remove "cpu" argument to rcu_preempt_check_callbacks() ...

sched: Add missing rcu protection to wake_up_all_idle_cpus

2014-12-08T10:44:19Z

Locklessly doing is_idle_task(rq->curr) is only okay because of RCU protection. The older variant of the broken code checked rq->curr == rq->idle instead and therefore didn't need RCU. Fixes: f6be8af1c95d ("sched: Add new API wake_up_if_idle() to wake up the idle cpu") Signed-off-by: Andy Lutomirski Reviewed-by: Chuansheng Liu Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/729365dddca178506dfd0a9451006344cd6808bc.1417277372.git.luto@amacapital.net Signed-off-by: Ingo Molnar

context_tracking: Restore previous state in schedule_user

2014-12-04T04:55:58Z

It appears that some SCHEDULE_USER (asm for schedule_user) callers in arch/x86/kernel/entry_64.S are called from RCU kernel context, and schedule_user will return in RCU user context. This causes RCU warnings and possible failures. This is intended to be a minimal fix suitable for 3.18. Reported-and-tested-by: Dave Jones Cc: Oleg Nesterov Cc: Frédéric Weisbecker Acked-by: Paul E. McKenney Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds