linux-kernel - Re: Can current macro be accessed from interrupt context?

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Date:	Fri, 23 Oct 2009 02:34:15 -0700
From:	"Leonidas ." <leonidas137@...il.com>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	Valdis.Kletnieks@...edu,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Can current macro be accessed from interrupt context?

> 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.
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