Re: use of preempt_count instead of in_atomic() at leds-gpio.c
[Posted March 24, 2008 by corbet]
| 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 |
| Message-ID: |
| <20080320164741.734e838c.akpm@linux-foundation.org> |
| 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> |
| Archive‑link: | |
Article |
On Thu, 20 Mar 2008 19:56:12 -0300 Henrique de Moraes Holschuh <hmh@hmh.eng.br> 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.