user/sven/linux.git/kernel/sched/wait.c, branch v5.2.2

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45Z

Add SPDX license identifiers to all files which: - Have no license information of any form - Have EXPORT_.*_SYMBOL_GPL inside which was used in the initial scan/conversion to ignore the file These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

kernel/sched/: remove caller signal_pending branch predictions

2019-01-04T21:13:48Z

This is already done for us internally by the signal machinery. Link: http://lkml.kernel.org/r/20181116002713.8474-3-dave@stgolabs.net Signed-off-by: Davidlohr Bueso Reviewed-by: Andrew Morton Cc: Peter Zijlstra Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sched/wait: assert the wait_queue_head lock is held in __wake_up_common

2018-08-22T17:52:47Z

Better ensure we actually hold the lock using lockdep than just commenting on it. Due to the various exported _locked interfaces it is far too easy to get the locking wrong. Link: http://lkml.kernel.org/r/20171214152344.6880-4-hch@lst.de Signed-off-by: Christoph Hellwig Acked-by: Ingo Molnar Cc: Al Viro Cc: Andrea Arcangeli Cc: Ingo Molnar Cc: Jason Baron Cc: Matthew Wilcox Cc: Mike Rapoport Cc: Peter Zijlstra Cc: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sched/Documentation: Update wake_up() & co. memory-barrier guarantees

2018-07-17T07:30:34Z

Both the implementation and the users' expectation [1] for the various wakeup primitives have evolved over time, but the documentation has not kept up with these changes: brings it into 2018. [1] http://lkml.kernel.org/r/20180424091510.GB4064@hirez.programming.kicks-ass.net Also applied feedback from Alan Stern. Suggested-by: Peter Zijlstra Signed-off-by: Andrea Parri Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra (Intel) Cc: Akira Yokosawa Cc: Alan Stern Cc: Boqun Feng Cc: Daniel Lustig Cc: David Howells Cc: Jade Alglave Cc: Jonathan Corbet Cc: Linus Torvalds Cc: Luc Maranget Cc: Nicholas Piggin Cc: Thomas Gleixner Cc: Will Deacon Cc: linux-arch@vger.kernel.org Cc: parri.andrea@gmail.com Link: http://lkml.kernel.org/r/20180716180605.16115-12-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

sched/core: Use smp_mb() in wake_woken_function()

2018-07-17T07:30:33Z

wake_woken_function() synchronizes with wait_woken() as follows: [wait_woken] [wake_woken_function] entry->flags &= ~wq_flag_woken; condition = true; smp_mb(); smp_wmb(); if (condition) wq_entry->flags |= wq_flag_woken; break; This commit replaces the above smp_wmb() with an smp_mb() in order to guarantee that either wait_woken() sees the wait condition being true or the store to wq_entry->flags in woken_wake_function() follows the store in wait_woken() in the coherence order (so that the former can eventually be observed by wait_woken()). The commit also fixes a comment associated to set_current_state() in wait_woken(): the comment pairs the barrier in set_current_state() to the above smp_wmb(), while the actual pairing involves the barrier in set_current_state() and the barrier executed by the try_to_wake_up() in wake_woken_function(). Signed-off-by: Andrea Parri Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/20180716180605.16115-10-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

sched/headers: Simplify and clean up header usage in the scheduler

2018-03-04T11:39:29Z

Do the following cleanups and simplifications: - sched/sched.h already includes , so no need to include it in sched/core.c again. - order the headers alphabetically - add all headers to kernel/sched/sched.h - remove all unnecessary includes from the .c files that are already included in kernel/sched/sched.h. Finally, make all scheduler .c files use a single common header: #include "sched.h" ... which now contains a union of the relied upon headers. This makes the various .c files easier to read and easier to handle. Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

sched: Clean up and harmonize the coding style of the scheduler code base

2018-03-03T14:50:21Z

A good number of small style inconsistencies have accumulated in the scheduler core, so do a pass over them to harmonize all these details: - fix speling in comments, - use curly braces for multi-line statements, - remove unnecessary parentheses from integer literals, - capitalize consistently, - remove stray newlines, - add comments where necessary, - remove invalid/unnecessary comments, - align structure definitions and other data types vertically, - add missing newlines for increased readability, - fix vertical tabulation where it's misaligned, - harmonize preprocessor conditional block labeling and vertical alignment, - remove line-breaks where they uglify the code, - add newline after local variable definitions, No change in functionality: md5: 1191fa0a890cfa8132156d2959d7e9e2 built-in.o.before.asm 1191fa0a890cfa8132156d2959d7e9e2 built-in.o.after.asm Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

sched/wait: Fix add_wait_queue() behavioral change

2017-12-06T18:30:34Z

The following cleanup commit: 50816c48997a ("sched/wait: Standardize internal naming of wait-queue entries") ... unintentionally changed the behavior of add_wait_queue() from inserting the wait entry at the head of the wait queue to the tail of the wait queue. Beyond a negative performance impact this change in behavior theoretically also breaks wait queues which mix exclusive and non-exclusive waiters, as non-exclusive waiters will not be woken up if they are queued behind enough exclusive waiters. Signed-off-by: Omar Sandoval Reviewed-by: Jens Axboe Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Thomas Gleixner Cc: kernel-team@fb.com Fixes: ("sched/wait: Standardize internal naming of wait-queue entries") Link: http://lkml.kernel.org/r/a16c8ccffd39bd08fdaa45a5192294c784b803a7.1512544324.git.osandov@fb.com Signed-off-by: Ingo Molnar

sched/wait: Introduce wakeup boomark in wake_up_page_bit

2017-09-14T16:56:18Z

Now that we have added breaks in the wait queue scan and allow bookmark on scan position, we put this logic in the wake_up_page_bit function. We can have very long page wait list in large system where multiple pages share the same wait list. We break the wake up walk here to allow other cpus a chance to access the list, and not to disable the interrupts when traversing the list for too long. This reduces the interrupt and rescheduling latency, and excessive page wait queue lock hold time. [ v2: Remove bookmark_wake_function ] Signed-off-by: Tim Chen Signed-off-by: Linus Torvalds

sched/wait: Break up long wake list walk

2017-09-14T16:56:17Z

We encountered workloads that have very long wake up list on large systems. A waker takes a long time to traverse the entire wake list and execute all the wake functions. We saw page wait list that are up to 3700+ entries long in tests of large 4 and 8 socket systems. It took 0.8 sec to traverse such list during wake up. Any other CPU that contends for the list spin lock will spin for a long time. It is a result of the numa balancing migration of hot pages that are shared by many threads. Multiple CPUs waking are queued up behind the lock, and the last one queued has to wait until all CPUs did all the wakeups. The page wait list is traversed with interrupt disabled, which caused various problems. This was the original cause that triggered the NMI watch dog timer in: https://patchwork.kernel.org/patch/9800303/ . Only extending the NMI watch dog timer there helped. This patch bookmarks the waker's scan position in wake list and break the wake up walk, to allow access to the list before the waker resume its walk down the rest of the wait list. It lowers the interrupt and rescheduling latency. This patch also provides a performance boost when combined with the next patch to break up page wakeup list walk. We saw 22% improvement in the will-it-scale file pread2 test on a Xeon Phi system running 256 threads. [ v2: Merged in Linus' changes to remove the bookmark_wake_function, and simply access to flags. ] Reported-by: Kan Liang Tested-by: Kan Liang Signed-off-by: Tim Chen Signed-off-by: Linus Torvalds