|From:||Andrew Morton <akpm-AT-linux-foundation.org>|
|To:||Henrique de Moraes Holschuh <hmh-AT-hmh.eng.br>|
|Subject:||Re: use of preempt_count instead of in_atomic() at leds-gpio.c|
|Date:||Thu, 20 Mar 2008 16:47:41 -0700|
|Cc:||David Brownell <david-b-AT-pacbell.net>, Richard Purdie <rpurdie-AT-rpsys.net>, linux-kernel-AT-vger.kernel.org, Ingo Molnar <mingo-AT-elte.hu>|
On Thu, 20 Mar 2008 19:56:12 -0300 Henrique de Moraes Holschuh <firstname.lastname@example.org> wrote: > Can we add "in_scheduleable()", or maybe "can_schedule()", that returns > in_atomic() if CONFIG_PREEMT, or 0 if there is no way to know? To my > limited knowledge of how that part of the kernel works, it would do the > right thing. If we did that, then people would use it. And that would be bad. It'll lead to code which behaves differently on non-preemptible kernels, to code which works less well on non-preemptible kernels and it will lead to less well-thought-out code in general. Really, this all points at an ill-designed part of the leds interface. The consistent pattern we use in the kernel is that callers keep track of whether they are running in a schedulable context and, if necessary, they will inform callees about that. Callees don't work it out for themselves.
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