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

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/wait: Introduce init_wait_entry()

2016-09-30T08:54:03Z

The partial initialization of wait_queue_t in prepare_to_wait_event() looks ugly. This was done to shrink .text, but we can simply add the new helper which does the full initialization and shrink the compiled code a bit more. And. This way prepare_to_wait_event() can have more users. In particular we are ready to remove the signal_pending_state() checks from wait_bit_action_f helpers and change __wait_on_bit_lock() to use prepare_to_wait_event(). Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Al Viro Cc: Bart Van Assche Cc: Johannes Weiner Cc: Linus Torvalds Cc: Mike Galbraith Cc: Neil Brown Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20160906140055.GA6167@redhat.com Signed-off-by: Ingo Molnar

sched/wait: Avoid abort_exclusive_wait() in __wait_on_bit_lock()

2016-09-30T08:54:03Z

__wait_on_bit_lock() doesn't need abort_exclusive_wait() too. Right now it can't use prepare_to_wait_event() (see the next change), but it can do the additional finish_wait() if action() fails. abort_exclusive_wait() no longer has callers, remove it. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Al Viro Cc: Bart Van Assche Cc: Johannes Weiner Cc: Linus Torvalds Cc: Mike Galbraith Cc: Neil Brown Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20160906140053.GA6164@redhat.com Signed-off-by: Ingo Molnar

sched/wait: Avoid abort_exclusive_wait() in ___wait_event()

2016-09-30T08:53:44Z

___wait_event() doesn't really need abort_exclusive_wait(), we can simply change prepare_to_wait_event() to remove the waiter from q->task_list if it was interrupted. This simplifies the code/logic, and this way prepare_to_wait_event() can have more users, see the next change. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Al Viro Cc: Bart Van Assche Cc: Johannes Weiner Cc: Linus Torvalds Cc: Mike Galbraith Cc: Neil Brown Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20160908164815.GA18801@redhat.com Signed-off-by: Ingo Molnar -- include/linux/wait.h | 7 +------ kernel/sched/wait.c | 35 +++++++++++++++++++++++++---------- 2 files changed, 26 insertions(+), 16 deletions(-)

sched/wait: Fix abort_exclusive_wait(), it should pass TASK_NORMAL to wake_up()

2016-09-30T08:53:19Z

Otherwise this logic only works if mode is "compatible" with another exclusive waiter. If some wq has both TASK_INTERRUPTIBLE and TASK_UNINTERRUPTIBLE waiters, abort_exclusive_wait() won't wait an uninterruptible waiter. The main user is __wait_on_bit_lock() and currently it is fine but only because TASK_KILLABLE includes TASK_UNINTERRUPTIBLE and we do not have lock_page_interruptible() yet. Just use TASK_NORMAL and remove the "mode" arg from abort_exclusive_wait(). Yes, this means that (say) wake_up_interruptible() can wake up the non- interruptible waiter(s), but I think this is fine. And in fact I think that abort_exclusive_wait() must die, see the next change. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Al Viro Cc: Bart Van Assche Cc: Johannes Weiner Cc: Linus Torvalds Cc: Mike Galbraith Cc: Neil Brown Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20160906140047.GA6157@redhat.com Signed-off-by: Ingo Molnar

sched/wait: Fix the signal handling fix

2015-12-13T22:30:59Z

Jan Stancek reported that I wrecked things for him by fixing things for Vladimir :/ His report was due to an UNINTERRUPTIBLE wait getting -EINTR, which should not be possible, however my previous patch made this possible by unconditionally checking signal_pending(). We cannot use current->state as was done previously, because the instruction after the store to that variable it can be changed. We must instead pass the initial state along and use that. Fixes: 68985633bccb ("sched/wait: Fix signal handling in bit wait helpers") Reported-by: Jan Stancek Reported-by: Chris Mason Tested-by: Jan Stancek Tested-by: Vladimir Murzin Tested-by: Chris Mason Reviewed-by: Paul Turner Cc: Ingo Molnar Cc: tglx@linutronix.de Cc: Oleg Nesterov Cc: hpa@zytor.com Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Linus Torvalds

sched/wait: Fix signal handling in bit wait helpers

2015-12-04T09:10:15Z

Vladimir reported getting RCU stall warnings and bisected it back to commit: 743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions") That commit inadvertently reversed the calls to schedule() and signal_pending(), thereby not handling the case where the signal receives while we sleep. Reported-by: Vladimir Murzin Tested-by: Vladimir Murzin Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: mark.rutland@arm.com Cc: neilb@suse.de Cc: oleg@redhat.com Fixes: 743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions") Fixes: cbbce8220949 ("SCHED: add some "wait..on_bit...timeout()" interfaces.") Link: http://lkml.kernel.org/r/20151201130404.GL3816@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar

userfaultfd: revert "userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key"

2015-09-22T22:09:53Z

This reverts commit 51360155eccb907ff8635bd10fc7de876408c2e0 and adapts fs/userfaultfd.c to use the old version of that function. It didn't look robust to call __wake_up_common with "nr == 1" when we absolutely require wakeall semantics, but we've full control of what we insert in the two waitqueue heads of the blocked userfaults. No exclusive waitqueue risks to be inserted into those two waitqueue heads so we can as well stick to "nr == 1" of the old code and we can rely purely on the fact no waitqueue inserted in one of the two waitqueue heads we must enforce as wakeall, has wait->flags WQ_FLAG_EXCLUSIVE set. Signed-off-by: Andrea Arcangeli Cc: Dr. David Alan Gilbert Cc: Michael Ellerman Cc: Shuah Khan Cc: Thierry Reding Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key

2015-09-04T23:54:41Z

userfaultfd needs to wake all waitqueues (pass 0 as nr parameter), instead of the current hardcoded 1 (that would wake just the first waitqueue in the head list). Signed-off-by: Andrea Arcangeli Acked-by: Pavel Emelyanov Cc: Sanidhya Kashyap Cc: zhang.zhanghailiang@huawei.com Cc: "Kirill A. Shutemov" Cc: Andres Lagar-Cavilla Cc: Dave Hansen Cc: Paolo Bonzini Cc: Rik van Riel Cc: Mel Gorman Cc: Andy Lutomirski Cc: Hugh Dickins Cc: Peter Feiner Cc: "Dr. David Alan Gilbert" Cc: Johannes Weiner Cc: "Huangpeng (Peter)" 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

2015-06-22T22:52:04Z

Pull scheduler updates from Ingo Molnar: "The main changes are: - lockless wakeup support for futexes and IPC message queues (Davidlohr Bueso, Peter Zijlstra) - Replace spinlocks with atomics in thread_group_cputimer(), to improve scalability (Jason Low) - NUMA balancing improvements (Rik van Riel) - SCHED_DEADLINE improvements (Wanpeng Li) - clean up and reorganize preemption helpers (Frederic Weisbecker) - decouple page fault disabling machinery from the preemption counter, to improve debuggability and robustness (David Hildenbrand) - SCHED_DEADLINE documentation updates (Luca Abeni) - topology CPU masks cleanups (Bartosz Golaszewski) - /proc/sched_debug improvements (Srikar Dronamraju)" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (79 commits) sched/deadline: Remove needless parameter in dl_runtime_exceeded() sched: Remove superfluous resetting of the p->dl_throttled flag sched/deadline: Drop duplicate init_sched_dl_class() declaration sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target sched/deadline: Make init_sched_dl_class() __init sched/deadline: Optimize pull_dl_task() sched/preempt: Add static_key() to preempt_notifiers sched/preempt: Fix preempt notifiers documentation about hlist_del() within unsafe iteration sched/stop_machine: Fix deadlock between multiple stop_two_cpus() sched/debug: Add sum_sleep_runtime to /proc//sched sched/debug: Replace vruntime with wait_sum in /proc/sched_debug sched/debug: Properly format runnable tasks in /proc/sched_debug sched/numa: Only consider less busy nodes as numa balancing destinations Revert 095bebf61a46 ("sched/numa: Do not move past the balance point if unbalanced") sched/fair: Prevent throttling in early pick_next_task_fair() preempt: Reorganize the notrace definitions a bit preempt: Use preempt_schedule_context() as the official tracing preemption point sched: Make preempt_schedule_context() function-tracing safe x86: Remove cpu_sibling_mask() and cpu_core_mask() x86: Replace cpu_**_mask() with topology_**_cpumask() ...