diff options
author | 2007-10-23 11:26:25 +0800 | |
---|---|---|
committer | 2007-10-23 09:01:31 -0700 | |
commit | a98ce5c6feead6bfedefabd46cb3d7f5be148d9a (patch) | |
tree | 7bbd027e40805966ad908e40f09ffd412a72a88b /kernel/irq | |
parent | Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmo... (diff) | |
download | linux-a98ce5c6feead6bfedefabd46cb3d7f5be148d9a.tar.gz linux-a98ce5c6feead6bfedefabd46cb3d7f5be148d9a.tar.bz2 linux-a98ce5c6feead6bfedefabd46cb3d7f5be148d9a.zip |
Fix synchronize_irq races with IRQ handler
As it is some callers of synchronize_irq rely on memory barriers
to provide synchronisation against the IRQ handlers. For example,
the tg3 driver does
tp->irq_sync = 1;
smp_mb();
synchronize_irq();
and then in the IRQ handler:
if (!tp->irq_sync)
netif_rx_schedule(dev, &tp->napi);
Unfortunately memory barriers only work well when they come in
pairs. Because we don't actually have memory barriers on the
IRQ path, the memory barrier before the synchronize_irq() doesn't
actually protect us.
In particular, synchronize_irq() may return followed by the
result of netif_rx_schedule being made visible.
This patch (mostly written by Linus) fixes this by using spin
locks instead of memory barries on the synchronize_irq() path.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/irq')
-rw-r--r-- | kernel/irq/manage.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 80eab7a04205..1f314221d534 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -29,12 +29,28 @@ void synchronize_irq(unsigned int irq) { struct irq_desc *desc = irq_desc + irq; + unsigned int status; if (irq >= NR_IRQS) return; - while (desc->status & IRQ_INPROGRESS) - cpu_relax(); + do { + unsigned long flags; + + /* + * Wait until we're out of the critical section. This might + * give the wrong answer due to the lack of memory barriers. + */ + while (desc->status & IRQ_INPROGRESS) + cpu_relax(); + + /* Ok, that indicated we're done: double-check carefully. */ + spin_lock_irqsave(&desc->lock, flags); + status = desc->status; + spin_unlock_irqrestore(&desc->lock, flags); + + /* Oops, that failed? */ + } while (status & IRQ_INPROGRESS); } EXPORT_SYMBOL(synchronize_irq); |