public inbox for linux-kernel@vger.kernel.org
 help / color / mirror / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: chengkaitao <pilgrimtao@gmail.com>
Cc: linux-kernel@vger.kernel.org, smuchun@gmail.com,
	Kaitao Cheng <pilgrimtao@gmail.com>
Subject: Re: [RESEND v2] irq: Refactor irq_wait_for_interrupt info to simplify the code
Date: Wed, 15 Jan 2020 14:43:14 +0100	[thread overview]
Message-ID: <877e1sg7il.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200106154430.3413-1-pilgrimtao@gmail.com>

chengkaitao <pilgrimtao@gmail.com> writes:
> From: Kaitao Cheng <pilgrimtao@gmail.com>
>
> Cleanup extra if(test_and_clear_bit), and put the other one in front.

That simplifies the code but opens a race window:

 CPU 0                                CPU 1
                                      irq_wait_for_interrupt()
                                        has not yet reached schedule()
 free_irq()
   remove_action();
   synchronize_irq();                   

   #ifdef CONFIG_DEBUG_SHIRQ
    action->handler()                   if (test_and_clear_bit())
                            ---> bit is not set yet                                           
      --> SET thread running
   #endif                               

   kthread_stop()                       if (kthread_stop())

                   ---> Leave with bit set and thread active count != 0

That's just the most obvious example...

Thanks,

        tglx

      reply	other threads:[~2020-01-15 13:43 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-06 15:44 [RESEND v2] irq: Refactor irq_wait_for_interrupt info to simplify the code chengkaitao
2020-01-15 13:43 ` Thomas Gleixner [this message]

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=877e1sg7il.fsf@nanos.tec.linutronix.de \
    --to=tglx@linutronix.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=pilgrimtao@gmail.com \
    --cc=smuchun@gmail.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