From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
valentin.schneider@arm.com,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH rcu/urgent 1/2] scftorture: Avoid false-positive warnings in scftorture_invoker()
Date: Wed, 14 Jul 2021 13:50:42 -0700 [thread overview]
Message-ID: <20210714205043.2033697-1-paulmck@kernel.org> (raw)
In-Reply-To: <20210714204928.GA2033276@paulmck-ThinkPad-P17-Gen-1>
If the call to set_cpus_allowed_ptr() in scftorture_invoker()
fails, a later WARN_ONCE() complains. But with the advent of
570a752b7a9b ("lib/smp_processor_id: Use is_percpu_thread() instead of
nr_cpus_allowed"), this complaint can be drowned out by complaints from
smp_processor_id(). The rationale for this change is that scftorture's
kthreads are not marked with PF_NO_SETAFFINITY, which means that a system
administrator could change affinity at any time.
However, scftorture is a torture test, and the system administrator might
well have a valid test-the-test reason for changing affinity. This commit
therefore changes to raw_smp_processor_id() in order to avoid the noise,
and also adds a WARN_ON_ONCE() to the call to set_cpus_allowed_ptr() in
order to directly detect immediate failure. There is no WARN_ON_ONCE()
within the test loop, allowing human-reflex-based affinity resetting,
if desired.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/scftorture.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 2377cbb32474..29e8fc5d91a7 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -405,15 +405,15 @@ static int scftorture_invoker(void *arg)
VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
cpu = scfp->cpu % nr_cpu_ids;
- set_cpus_allowed_ptr(current, cpumask_of(cpu));
+ WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(cpu)));
set_user_nice(current, MAX_NICE);
if (holdoff)
schedule_timeout_interruptible(holdoff * HZ);
- VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());
+ VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, raw_smp_processor_id());
// Make sure that the CPU is affinitized appropriately during testing.
- curcpu = smp_processor_id();
+ curcpu = raw_smp_processor_id();
WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
"%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
__func__, scfp->cpu, curcpu, nr_cpu_ids);
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2021-07-14 20:50 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 20:49 [PATCH rcu/urgent 0/2] Adjust for updated scheduler CPU-affinity semantics Paul E. McKenney
2021-07-14 20:50 ` Paul E. McKenney [this message]
2021-07-14 20:50 ` [PATCH rcu/urgent 2/2] refscale: Avoid false-positive warnings in ref_scale_reader() Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210714205043.2033697-1-paulmck@kernel.org \
--to=paulmck@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=dhowells@redhat.com \
--cc=edumazet@google.com \
--cc=fweisbec@gmail.com \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=valentin.schneider@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).