user/sven/linux.git/kernel/sched, branch v4.9.5

sched/autogroup: Fix 64-bit kernel nice level adjustment

2016-11-24T04:45:02Z

Michael Kerrisk reported: > Regarding the previous paragraph... My tests indicate > that writing *any* value to the autogroup [nice priority level] > file causes the task group to get a lower priority. Because autogroup didn't call the then meaningless scale_load()... Autogroup nice level adjustment has been broken ever since load resolution was increased for 64-bit kernels. Use scale_load() to scale group weight. Michael Kerrisk tested this patch to fix the problem: > Applied and tested against 4.9-rc6 on an Intel u7 (4 cores). > Test setup: > > Terminal window 1: running 40 CPU burner jobs > Terminal window 2: running 40 CPU burner jobs > Terminal window 1: running 1 CPU burner job > > Demonstrated that: > * Writing "0" to the autogroup file for TW1 now causes no change > to the rate at which the process on the terminal consume CPU. > * Writing -20 to the autogroup file for TW1 caused those processes > to get the lion's share of CPU while TW2 TW3 get a tiny amount. > * Writing -20 to the autogroup files for TW1 and TW3 allowed the > process on TW3 to get as much CPU as it was getting as when > the autogroup nice values for both terminals were 0. Reported-by: Michael Kerrisk Tested-by: Michael Kerrisk Signed-off-by: Mike Galbraith Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-man Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1479897217.4306.6.camel@gmx.de Signed-off-by: Ingo Molnar

sched/autogroup: Do not use autogroup->tg in zombie threads

2016-11-22T11:33:43Z

Exactly because for_each_thread() in autogroup_move_group() can't see it and update its ->sched_task_group before _put() and possibly free(). So the exiting task needs another sched_move_task() before exit_notify() and we need to re-introduce the PF_EXITING (or similar) check removed by the previous change for another reason. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: hartsjc@redhat.com Cc: vbendel@redhat.com Cc: vlovejoy@redhat.com Link: http://lkml.kernel.org/r/20161114184612.GA15968@redhat.com Signed-off-by: Ingo Molnar

sched/autogroup: Fix autogroup_move_group() to never skip sched_move_task()

2016-11-22T11:33:42Z

The PF_EXITING check in task_wants_autogroup() is no longer needed. Remove it, but see the next patch. However the comment is correct in that autogroup_move_group() must always change task_group() for every thread so the sysctl_ check is very wrong; we can race with cgroups and even sys_setsid() is not safe because a task running with task_group() == ag->tg must participate in refcounting: int main(void) { int sctl = open("/proc/sys/kernel/sched_autogroup_enabled", O_WRONLY); assert(sctl > 0); if (fork()) { wait(NULL); // destroy the child's ag/tg pause(); } assert(pwrite(sctl, "1\n", 2, 0) == 2); assert(setsid() > 0); if (fork()) pause(); kill(getppid(), SIGKILL); sleep(1); // The child has gone, the grandchild runs with kref == 1 assert(pwrite(sctl, "0\n", 2, 0) == 2); assert(setsid() > 0); // runs with the freed ag/tg for (;;) sleep(1); return 0; } crashes the kernel. It doesn't really need sleep(1), it doesn't matter if autogroup_move_group() actually frees the task_group or this happens later. Reported-by: Vern Lovejoy Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: hartsjc@redhat.com Cc: vbendel@redhat.com Link: http://lkml.kernel.org/r/20161114184609.GA15965@redhat.com Signed-off-by: Ingo Molnar

sched/core: Remove pointless printout in sched_show_task()

2016-11-03T06:31:34Z

In sched_show_task() we print out a useless hex number, not even a symbol, and there's a big question mark whether this even makes sense anyway, I suspect we should just remove it all. Signed-off-by: Linus Torvalds Acked-by: Andy Lutomirski Cc: Peter Zijlstra Cc: Tetsuo Handa Cc: Thomas Gleixner Cc: bp@alien8.de Cc: brgerst@gmail.com Cc: jann@thejh.net Cc: keescook@chromium.org Cc: linux-api@vger.kernel.org Cc: tycho.andersen@canonical.com Link: http://lkml.kernel.org/r/CA+55aFzphURPFzAvU4z6Moy7ZmimcwPuUdYU8bj9z0J+S8X1rw@mail.gmail.com Signed-off-by: Ingo Molnar

sched/core: Fix oops in sched_show_task()

2016-11-03T06:27:34Z

When CONFIG_THREAD_INFO_IN_TASK=y, it is possible that an exited thread remains in the task list after its stack pointer was already set to NULL. Therefore, thread_saved_pc() and stack_not_used() in sched_show_task() will trigger NULL pointer dereference if an attempt to dump such thread's traces (e.g. SysRq-t, khungtaskd) is made. Since show_stack() in sched_show_task() calls try_get_task_stack() and sched_show_task() is called from interrupt context, calling try_get_task_stack() from sched_show_task() will be safe as well. Signed-off-by: Tetsuo Handa Acked-by: Andy Lutomirski Acked-by: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bp@alien8.de Cc: brgerst@gmail.com Cc: jann@thejh.net Cc: keescook@chromium.org Cc: linux-api@vger.kernel.org Cc: tycho.andersen@canonical.com Link: http://lkml.kernel.org/r/201611021950.FEJ34368.HFFJOOMLtQOVSF@I-love.SAKURA.ne.jp Signed-off-by: Ingo Molnar

Merge branches 'core-urgent-for-linus', 'irq-urgent-for-linus' and 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2016-10-28T17:12:27Z

Pull objtool, irq and scheduler fixes from Ingo Molnar: "One more objtool fixlet for GCC6 code generation patterns, an irq DocBook fix and an unused variable warning fix in the scheduler" * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: objtool: Fix rare switch jump table pattern detection * 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: doc: Add missing parameter for msi_setup * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/fair: Remove unused but set variable 'rq'

mm: remove per-zone hashtable of bitlock waitqueues

2016-10-27T16:27:57Z

The per-zone waitqueues exist because of a scalability issue with the page waitqueues on some NUMA machines, but it turns out that they hurt normal loads, and now with the vmalloced stacks they also end up breaking gfs2 that uses a bit_wait on a stack object: wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE) where 'gh' can be a reference to the local variable 'mount_gh' on the stack of fill_super(). The reason the per-zone hash table breaks for this case is that there is no "zone" for virtual allocations, and trying to look up the physical page to get at it will fail (with a BUG_ON()). It turns out that I actually complained to the mm people about the per-zone hash table for another reason just a month ago: the zone lookup also hurts the regular use of "unlock_page()" a lot, because the zone lookup ends up forcing several unnecessary cache misses and generates horrible code. As part of that earlier discussion, we had a much better solution for the NUMA scalability issue - by just making the page lock have a separate contention bit, the waitqueue doesn't even have to be looked at for the normal case. Peter Zijlstra already has a patch for that, but let's see if anybody even notices. In the meantime, let's fix the actual gfs2 breakage by simplifying the bitlock waitqueues and removing the per-zone issue. Reported-by: Andreas Gruenbacher Tested-by: Bob Peterson Acked-by: Mel Gorman Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Steven Whitehouse Signed-off-by: Linus Torvalds

sched/fair: Remove unused but set variable 'rq'

2016-10-27T06:33:52Z

Since commit: 8663e24d56dc ("sched/fair: Reorder cgroup creation code") ... the variable 'rq' in alloc_fair_sched_group() is set but no longer used. Remove it to fix the following GCC warning when building with 'W=1': kernel/sched/fair.c:8842:13: warning: variable ‘rq’ set but not used [-Wunused-but-set-variable] Signed-off-by: Tobias Klauser Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20161026113704.8981-1-tklauser@distanz.ch Signed-off-by: Ingo Molnar

sched/fair: Fix incorrect task group ->load_avg

2016-10-19T13:04:47Z

A scheduler performance regression has been reported by Joseph Salisbury, which he bisected back to: 3d30544f0212 ("sched/fair: Apply more PELT fixes) The regression triggers when several levels of task groups are involved (read: SystemD) and cpu_possible_mask != cpu_present_mask. The root cause is that group entity's load (tg_child->se[i]->avg.load_avg) is initialized to scale_load_down(se->load.weight). During the creation of a child task group, its group entities on possible CPUs are attached to parent's cfs_rq (tg_parent) and their loads are added to the parent's load (tg_parent->load_avg) with update_tg_load_avg(). But only the load on online CPUs will then be updated to reflect real load, whereas load on other CPUs will stay at the initial value. The result is a tg_parent->load_avg that is higher than the real load, the weight of group entities (tg_parent->se[i]->load.weight) on online CPUs is smaller than it should be, and the task group gets a less running time than what it could expect. ( This situation can be detected with /proc/sched_debug. The ".tg_load_avg" of the task group will be much higher than sum of ".tg_load_avg_contrib" of online cfs_rqs of the task group. ) The load of group entities don't have to be intialized to something else than 0 because their load will increase when an entity is attached. Reported-by: Joseph Salisbury Tested-by: Dietmar Eggemann Signed-off-by: Vincent Guittot Acked-by: Peter Zijlstra Cc: # 4.8.x Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: joonwoop@codeaurora.org Fixes: 3d30544f0212 ("sched/fair: Apply more PELT fixes) Link: http://lkml.kernel.org/r/1476881123-10159-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar

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

2016-10-18T16:53:59Z

Pull scheduler fix from Ingo Molnar: "Fix a crash that can trigger when racing with CPU hotplug: we didn't use sched-domains data structures carefully enough in select_idle_cpu()" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/fair: Fix sched domains NULL dereference in select_idle_sibling()