From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp08.au.ibm.com (e23smtp08.au.ibm.com [202.81.31.141]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp08.au.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id C73D3B7071 for ; Thu, 19 Apr 2012 19:04:54 +1000 (EST) Received: from /spool/local by e23smtp08.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 19 Apr 2012 08:18:58 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q3J8DBOr1740808 for ; Thu, 19 Apr 2012 18:13:11 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q3J8JmM6008291 for ; Thu, 19 Apr 2012 18:19:49 +1000 From: Benjamin Herrenschmidt To: linuxppc-dev@ozlabs.org Subject: [PATCH 07/15] powerpc/pmac: Don't add_timer() twice Date: Thu, 19 Apr 2012 18:16:48 +1000 Message-Id: <1334823416-9138-8-git-send-email-benh@kernel.crashing.org> In-Reply-To: <1334823416-9138-1-git-send-email-benh@kernel.crashing.org> References: <1334823416-9138-1-git-send-email-benh@kernel.crashing.org> Cc: khali@linux-fr.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 f991dbb..fc536f2 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); } -- 1.7.9.5