All of lore.kernel.org
 help / color / mirror / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: Qian Cai <cai@lca.pw>, fweisbec@gmail.com, mingo@kernel.org
Cc: elver@google.com, linux-kernel@vger.kernel.org,
	Qian Cai <cai@lca.pw>, Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] tick/sched: fix data races at tick_do_timer_cpu
Date: Wed, 04 Mar 2020 10:39:41 +0100	[thread overview]
Message-ID: <87tv34laqq.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200225030808.1207-1-cai@lca.pw>

Qian,

Qian Cai <cai@lca.pw> writes:
> tick_do_timer_cpu could be accessed concurrently where both plain writes
> and plain reads are not protected by a lock. Thus, it could result in
> data races. Fix them by adding pairs of READ|WRITE_ONCE(). The data
> races were reported by KCSAN,

They are reported, but are they actually a real problem?

This completely lacks analysis why these 8 places need the
READ/WRITE_ONCE() treatment at all and if so why the other 14 places
accessing tick_do_timer_cpu are safe without it.

I definitely appreciate the work done with KCSAN, but just making the
tool shut up does not cut it. 

Thanks,

        tglx

  reply	other threads:[~2020-03-04  9:39 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-25  3:08 [PATCH] tick/sched: fix data races at tick_do_timer_cpu Qian Cai
2020-03-04  9:39 ` Thomas Gleixner [this message]
2020-03-04  9:56   ` Peter Zijlstra
2020-03-04 11:24     ` Qian Cai
2020-03-04 11:20   ` Qian Cai
2020-03-06 15:02     ` Qian Cai
2020-03-07  0:45       ` Thomas Gleixner

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=87tv34laqq.fsf@nanos.tec.linutronix.de \
    --to=tglx@linutronix.de \
    --cc=cai@lca.pw \
    --cc=elver@google.com \
    --cc=fweisbec@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.