From: Robert Love <rml@tech9.net>
To: Pavel Machek <pavel@ucw.cz>
Cc: kernel list <linux-kernel@vger.kernel.org>
Subject: Re: in_atomic() & spin_lock / spin_unlock in different functions
Date: 13 Oct 2002 15:40:09 -0400 [thread overview]
Message-ID: <1034538009.753.4507.camel@phantasy> (raw)
In-Reply-To: <20021013203838.A122@elf.ucw.cz>
On Sun, 2002-10-13 at 14:38, Pavel Machek wrote:
> I'm doing spin_lock_irqsave() then in another function
> spin_unlock_irqrestore. Is that okay? If no, can it cause "scheduling
> in atomic"?
It is not OK if the function is run by a different process. Then one
process will have a preempt_count one larger than it should and one
would have a preempt_count one smaller.
The task with the one smaller preempt_count will probably cause a crash
when it preemptively reschedules erroneously.
In other words, you have:
Process A Process B
preempt_count++
preempt_count--
When both of those routines need to be done by the same process.
Also, you cannot use spin_lock_irqsave() in different functions at all
on sparc as it contains stack information.
Robert Love
next prev parent reply other threads:[~2002-10-13 19:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-13 18:38 in_atomic() & spin_lock / spin_unlock in different functions Pavel Machek
2002-10-13 19:40 ` Robert Love [this message]
2002-10-13 19:21 Manfred Spraul
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