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powerpc/pmac: Don't add_timer() twice

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If the interrupt and the timeout happen roughly at the same
time, we can get into a situation where the timer function
is run while the interrupt has already been processed. In
this case, the timer function might end up doing an add_timer
on an already pending timer, causing a BUG_ON() to trigger.

Instead, just skip the whole timeout operation if we see that
the timer is pending. The spinlock ensures that the only way
that happens is if we already started a new operation and thus
the timeout can be ignored.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2012-04-18 22:16:48 +00:00
parent 2ef822c553
commit 3027691e58
1 changed files with 9 additions and 0 deletions
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9
arch/powerpc/platforms/powermac/low_i2c.c
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@ -366,11 +366,20 @@ static void kw_i2c_timeout(unsigned long data)
unsigned long flags;
spin_lock_irqsave(&host->lock, flags);
/*
* If the timer is pending, that means we raced with the
* irq, in which case we just return
*/
if (timer_pending(&host->timeout_timer))
goto skip;
kw_i2c_handle_interrupt(host, kw_read_reg(reg_isr));
if (host->state != state_idle) {
host->timeout_timer.expires = jiffies + KW_POLL_TIMEOUT;
add_timer(&host->timeout_timer);
}
skip:
spin_unlock_irqrestore(&host->lock, flags);
}