user/sven/linux.git/kernel/sched.c, branch v3.2.76

sched/core: Clear the root_domain cpumasks in init_rootdomain()

2015-12-30T02:26:00Z

commit 8295c69925ad53ec32ca54ac9fc194ff21bc40e2 upstream. root_domain::rto_mask allocated through alloc_cpumask_var() contains garbage data, this may cause problems. For instance, When doing pull_rt_task(), it may do useless iterations if rto_mask retains some extra garbage bits. Worse still, this violates the isolated domain rule for clustered scheduling using cpuset, because the tasks(with all the cpus allowed) belongs to one root domain can be pulled away into another root domain. The patch cleans the garbage by using zalloc_cpumask_var() instead of alloc_cpumask_var() for root_domain::rto_mask allocation, thereby addressing the issues. Do the same thing for root_domain's other cpumask memembers: dlo_mask, span, and online. Signed-off-by: Xunlei Pang Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1449057179-29321-1-git-send-email-xlpang@redhat.com Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: - There's no dlo_mask to initialise - Adjust filename] Signed-off-by: Ben Hutchings

sched/core: Remove false-positive warning from wake_up_process()

2015-12-30T02:26:00Z

commit 119d6f6a3be8b424b200dcee56e74484d5445f7e upstream. Because wakeups can (fundamentally) be late, a task might not be in the expected state. Therefore testing against a task's state is racy, and can yield false positives. Signed-off-by: Sasha Levin Signed-off-by: Peter Zijlstra (Intel) Acked-by: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: oleg@redhat.com Fixes: 9067ac85d533 ("wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task") Link: http://lkml.kernel.org/r/1448933660-23082-1-git-send-email-sasha.levin@oracle.com Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings

sched/core: Fix TASK_DEAD race in finish_task_switch()

2015-11-17T15:54:43Z

commit 95913d97914f44db2b81271c2e2ebd4d2ac2df83 upstream. So the problem this patch is trying to address is as follows: CPU0 CPU1 context_switch(A, B) ttwu(A) LOCK A->pi_lock A->on_cpu == 0 finish_task_switch(A) prev_state = A->state <-. WMB | A->on_cpu = 0; | UNLOCK rq0->lock | | context_switch(C, A) `-- A->state = TASK_DEAD prev_state == TASK_DEAD put_task_struct(A) context_switch(A, C) finish_task_switch(A) A->state == TASK_DEAD put_task_struct(A) The argument being that the WMB will allow the load of A->state on CPU0 to cross over and observe CPU1's store of A->state, which will then result in a double-drop and use-after-free. Now the comment states (and this was true once upon a long time ago) that we need to observe A->state while holding rq->lock because that will order us against the wakeup; however the wakeup will not in fact acquire (that) rq->lock; it takes A->pi_lock these days. We can obviously fix this by upgrading the WMB to an MB, but that is expensive, so we'd rather avoid that. The alternative this patch takes is: smp_store_release(&A->on_cpu, 0), which avoids the MB on some archs, but not important ones like ARM. Reported-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Acked-by: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Cc: manfred@colorfullife.com Cc: will.deacon@arm.com Fixes: e4a52bcb9a18 ("sched: Remove rq->lock from the first half of ttwu()") Link: http://lkml.kernel.org/r/20150929124509.GG3816@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: - Adjust filename - As smp_store_release() is not defined, use smp_mb()] Signed-off-by: Ben Hutchings

sched: Fix RLIMIT_RTTIME when PI-boosting to RT

2015-05-09T22:16:32Z

commit 746db9443ea57fd9c059f62c4bfbf41cf224fe13 upstream. When non-realtime tasks get priority-inheritance boosted to a realtime scheduling class, RLIMIT_RTTIME starts to apply to them. However, the counter used for checking this (the same one used for SCHED_RR timeslices) was not getting reset. This meant that tasks running with a non-realtime scheduling class which are repeatedly boosted to a realtime one, but never block while they are running realtime, eventually hit the timeout without ever running for a time over the limit. This patch resets the realtime timeslice counter when un-PI-boosting from an RT to a non-RT scheduling class. I have some test code with two threads and a shared PTHREAD_PRIO_INHERIT mutex which induces priority boosting and spins while boosted that gets killed by a SIGXCPU on non-fixed kernels but doesn't with this patch applied. It happens much faster with a CONFIG_PREEMPT_RT kernel, and does happen eventually with PREEMPT_VOLUNTARY kernels. Signed-off-by: Brian Silverman Signed-off-by: Peter Zijlstra (Intel) Cc: austin@peloton-tech.com Link: http://lkml.kernel.org/r/1424305436-6716-1-git-send-email-brian@peloton-tech.com Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filename, context] Signed-off-by: Ben Hutchings

sched/autogroup: Fix failure to set cpu.rt_runtime_us

2015-05-09T22:16:18Z

commit 1fe89e1b6d270aa0d3452c60d38461ea589594e3 upstream. Because task_group() uses a cache of autogroup_task_group(), whose output depends on sched_class, switching classes can generate problems. In particular, when started as fair, the cache points to the autogroup, so when switching to RT the tg_rt_schedulable() test fails for every cpu.rt_{runtime,period}_us change because now the autogroup has tasks and no runtime. Furthermore, going back to the previous semantics of varying task_group() with sched_class has the down-side that the sched_debug output varies as well, even though the task really is in the autogroup. Therefore add an autogroup exception to tg_has_rt_tasks() -- such that both (all) task_group() usages in sched/core now have one. And remove all the remnants of the variable task_group() output. Reported-by: Zefan Li Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Stefan Bader Fixes: 8323f26ce342 ("sched: Fix race in task_group()") Link: http://lkml.kernel.org/r/20150209112237.GR5029@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filenames, context] Signed-off-by: Ben Hutchings

sched: Unthrottle rt runqueues in __disable_runtime()

2014-02-15T19:20:18Z

commit a4c96ae319b8047f62dedbe1eac79e321c185749 upstream. migrate_tasks() uses _pick_next_task_rt() to get tasks from the real-time runqueues to be migrated. When rt_rq is throttled _pick_next_task_rt() won't return anything, in which case migrate_tasks() can't move all threads over and gets stuck in an infinite loop. Instead unthrottle rt runqueues before migrating tasks. Additionally: move unthrottle_offline_cfs_rqs() to rq_offline_fair() Signed-off-by: Peter Boonstoppel Signed-off-by: Peter Zijlstra Cc: Paul Turner Link: http://lkml.kernel.org/r/5FBF8E85CA34454794F0F7ECBA79798F379D3648B7@HQMAIL04.nvidia.com Signed-off-by: Ingo Molnar [ lizf: backported to 3.4: adjust context ] Signed-off-by: Li Zefan [bwh: Backported to 3.2: - Adjust filenames - unthrottle_offline_cfs_rqs() is already static, but defined in sched.c after including sched_fair.c, so add forward declaration - unthrottle_offline_cfs_rqs() also needs to be defined for all CONFIG_SMP configurations now] Signed-off-by: Ben Hutchings

sched/debug: Fix sd->*_idx limit range avoiding overflow

2013-05-30T13:35:09Z

commit fd9b86d37a600488dbd80fe60cca46b822bff1cd upstream. Commit 201c373e8e ("sched/debug: Limit sd->*_idx range on sysctl") was an incomplete bug fix. This patch fixes sd->*_idx limit range to [0 ~ CPU_LOAD_IDX_MAX-1] avoiding array overflow caused by setting sd->*_idx to CPU_LOAD_IDX_MAX on sysctl. Signed-off-by: Libin Cc: Cc: Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/51626610.2040607@huawei.com Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings

sched/debug: Limit sd->*_idx range on sysctl

2013-05-30T13:35:09Z

commit 201c373e8e4823700d3160d5c28e1ab18fd1193e upstream. Various sd->*_idx's are used for refering the rq's load average table when selecting a cpu to run. However they can be set to any number with sysctl knobs so that it can crash the kernel if something bad is given. Fix it by limiting them into the actual range. Signed-off-by: Namhyung Kim Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1345104204-8317-1-git-send-email-namhyung@kernel.org Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: - Adjust filename - s/umode_t/mode_t/] Signed-off-by: Ben Hutchings

sched: Convert BUG_ON()s in try_to_wake_up_local() to WARN_ON_ONCE()s

2013-04-25T19:25:51Z

commit 383efcd00053ec40023010ce5034bd702e7ab373 upstream. try_to_wake_up_local() should only be invoked to wake up another task in the same runqueue and BUG_ON()s are used to enforce the rule. Missing try_to_wake_up_local() can stall workqueue execution but such stalls are likely to be finite either by another work item being queued or the one blocked getting unblocked. There's no reason to trigger BUG while holding rq lock crashing the whole system. Convert BUG_ON()s in try_to_wake_up_local() to WARN_ON_ONCE()s. Signed-off-by: Tejun Heo Acked-by: Steven Rostedt Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20130318192234.GD3042@htj.dyndns.org Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings

wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task

2013-02-20T03:15:30Z

commit 9067ac85d533651b98c2ff903182a20cbb361fcb upstream. wake_up_process() should never wakeup a TASK_STOPPED/TRACED task. Change it to use TASK_NORMAL and add the WARN_ON(). TASK_ALL has no other users, probably can be killed. Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings