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genirq: warn when IRQF_DISABLED may be ignored 

Impact: emit new warning

We periodically waste time tracking down problems from the genirq
framework not respecting IRQF_DISABLED for some shared IRQ cases.  Linus
views this as "will not fix", but we're still left with the bugs caused by
this misbehavior.

This patch adds a nag message in request_irq(), so that drivers can fix
their IRQ handlers to avoid this problem.

Note that developers will never see the relevant bugs when they run with
LOCKDEP, so it's no wonder these bugs are hard to find.  (That also means
LOCKDEP is overlooking some IRQ-related bugs involving IRQ handlers that
don't set IRQF_DISABLED...)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
David Brownell 2008-12-01 14:31:37 -08:00 committed by Ingo Molnar
parent 7807fafa52
commit 470c66239e
1 changed files with 12 additions and 0 deletions
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12
kernel/irq/manage.c
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@ -635,6 +635,18 @@ int request_irq(unsigned int irq, irq_handler_t handler,
struct irq_desc *desc;
int retval;
/*
* handle_IRQ_event() always ignores IRQF_DISABLED except for
* the _first_ irqaction (sigh). That can cause oopsing, but
* the behavior is classified as "will not fix" so we need to
* start nudging drivers away from using that idiom.
*/
if ((irqflags & (IRQF_SHARED|IRQF_DISABLED))
== (IRQF_SHARED|IRQF_DISABLED))
pr_warning("IRQ %d/%s: IRQF_DISABLED is not "
"guaranteed on shared IRQs\n",
irq, devname);
#ifdef CONFIG_LOCKDEP
/*
* Lockdep wants atomic interrupt handlers: