From 3027691e58bfb21f6ea2e9f1d225d11b4e2b20e2 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Wed, 18 Apr 2012 22:16:48 +0000 Subject: [PATCH] powerpc/pmac: Don't add_timer() twice 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 --- arch/powerpc/platforms/powermac/low_i2c.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/powerpc/platforms/powermac/low_i2c.c b/arch/powerpc/platforms/powermac/low_i2c.c index 996c5ff7824b..03685a329d7d 100644 --- a/arch/powerpc/platforms/powermac/low_i2c.c +++ b/arch/powerpc/platforms/powermac/low_i2c.c @@ -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); } -- 2.20.1