linux-kernel - Re: [GIT PULL v2] Scheduler enhancements for v6.14

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Message-ID: <Z5AKKBpk8EUF6MSe@gmail.com>
Date: Tue, 21 Jan 2025 21:57:12 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Michael Jeanson <mjeanson@...icios.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>, Tejun Heo <tj@...nel.org>
Subject: Re: [GIT PULL v2] Scheduler enhancements for v6.14


* Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> > > Since I booted the scheduler tree on generic desktops and it was 
> > > tested on other systems as well and nothing appeared to be 
> > > broken, I presume RSEQ_FLAG_UNREGISTER is used only in libc 
> > > syscall-testcases and in specific applications?
> > 
> > Nowadays, rseq unregistration is used by specialized applications 
> > (e.g. tcmalloc) which disable glibc rseq support with the glibc 
> > tunable and register it themselves. 
> > (GLIBC_TUNABLES=glibc.pthread.rseq=0)
> > 
> > A recent glibc (2.35+) don't use explicit rseq unregistration, it's 
> > unregistered implicitly when the thread exits.
> > 
> > I'll make a note to add a test case for 
> > GLIBC_TUNABLES=glibc.pthread.rseq=0 in the rseq selftests and 
> > librseq to improve test coverage when using a recent glibc.
> > 
> > We have all the code in there to use rseq unregistration, but it is 
> > skipped when glibc 2.35+ is handling the registration.
> 
> It turns out that it is covered by both librseq and glibc tests, just 
> not by the kernel rseq selftests:
> 
> librseq test: tests/syscall_errors_test.c
> glibc test: sysdeps/unix/sysv/linux/tst-rseq-disable.c
> 
> We should import the librseq test into the kernel rseq selftests as
> well. CCing Michael Jeanson who will take care of this.

Thank you! Linus just pulled the v2 pull request, so all should be good 
upstream.

	Ingo