linux-kernel - [GIT PULL] posix-cpu-timers leftover overhead fixes

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Message-Id: <20210726125513.271824-1-frederic@kernel.org>
Date:   Mon, 26 Jul 2021 14:55:07 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>
Subject: [GIT PULL] posix-cpu-timers leftover overhead fixes

Thomas, Ingo,

Please pull the timers/core branch that can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	timers/core

HEAD: 63a17eea7d5516f9e927fdc52b45f1d040fdcf35

---

Those are not regression fixes since these bugs precede the git-era,
therefore they are not carrying a stable tag.

Several posix cpu timers events (setting, deletion, expiration) may end
up leaving needless elapsing overhead after a timer has stopped or
even after it has been deleted. Those overhead are:

1) Costly process wide cputime accounting that rely on concurrent atomic
addition during tick or even more frequent scheduler internal stat updates.

2) Retained tick dependency on NOHZ_FULL configurations.

Hopefully this series gets rid of all the possible culprits.

Thanks,
	Frederic
---

Frederic Weisbecker (6):
      posix-cpu-timers: Assert task sighand is locked while starting cputime counter
      posix-cpu-timers: Force next_expiration recalc after timer deletion
      posix-cpu-timers: Force next expiration recalc after itimer reset
      posix-cpu-timers: Remove confusing error code override
      posix-cpu-timers: Consolidate timer base accessor
      posix-cpu-timers: Recalc next expiration when timer_settime() ends up not queueing

 include/linux/posix-timers.h   | 11 +++++-
 include/linux/sched/signal.h   |  6 +++
 kernel/signal.c                | 15 +++++++
 kernel/time/posix-cpu-timers.c | 90 ++++++++++++++++++++++++++++++++++--------
 4 files changed, 103 insertions(+), 19 deletions(-)