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From: "Leonidas ." <leonidas137@gmail.com>
To: Clemens Ladisch <clemens@ladisch.de>
Cc: Valdis.Kletnieks@vt.edu, linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Can current macro be accessed from interrupt context?
Date: Fri, 23 Oct 2009 02:34:15 -0700	[thread overview]
Message-ID: <f22d86810910230234qed58b28g920a98bb3720b146@mail.gmail.com> (raw)
In-Reply-To: <4AE165A1.5080204@ladisch.de>

> There is no fixed association between your tasks and the CPUs they are
> running on.  It is possible for two of your threads to be executed on
> the same CPU (one after the other), or for one thread to migrate between
> CPUs.

Yes, you are right. I had not thought about thread migration etc and was
painting a rather simple picture of things.

>
> The task that was interrupted is probably some entirely different task
> (the X server, the shell, your mail reader, some kernel thread, or
> any of the other tasks running on your system).
>
> It is possible for your interrupt handler to be called for some device
> request that belongs to one of your tasks that is currently running on
> another CPU, so you won't be able to manage that data without locking.
>

Yes, this is pretty much points towards using per-cpu data.
Seems like my thought experiment will lead to an early demise.

Thanks for the explanation.


-Leo.

      reply	other threads:[~2009-10-23  9:34 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-10-22 11:10 Leonidas .
2009-10-22 11:27 ` Frederic Weisbecker
2009-10-22 11:43   ` Leonidas .
2009-10-22 11:49     ` Leonidas .
2009-10-22 12:06     ` Frederic Weisbecker
2009-10-22 13:37       ` Leonidas .
2009-10-22 13:45 ` Arjan van de Ven
2009-10-22 15:17 ` Valdis.Kletnieks
2009-10-22 17:46   ` Leonidas .
2009-10-22 18:12     ` Leonidas .
2009-10-23  8:13     ` Clemens Ladisch
2009-10-23  9:34       ` Leonidas . [this message]

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