This is a note to let you know that I've just added the patch titled
i2c-algo-bit: Fix spurious SCL timeouts under heavy load
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-algo-bit-fix-spurious-scl-timeouts-under-heavy-load.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 8ee161ce5e0cfc689eb677f227a6248191165fac Mon Sep 17 00:00:00 2001
From: Ville Syrjala <[email protected]>
Date: Thu, 15 Mar 2012 18:11:05 +0100
Subject: i2c-algo-bit: Fix spurious SCL timeouts under heavy load
From: Ville Syrjala <[email protected]>
commit 8ee161ce5e0cfc689eb677f227a6248191165fac upstream.
When the system is under heavy load, there can be a significant delay
between the getscl() and time_after() calls inside sclhi(). That delay
may cause the time_after() check to trigger after SCL has gone high,
causing sclhi() to return -ETIMEDOUT.
To fix the problem, double check that SCL is still low after the
timeout has been reached, before deciding to return -ETIMEDOUT.
Signed-off-by: Ville Syrjala <[email protected]>
Signed-off-by: Jean Delvare <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/i2c/algos/i2c-algo-bit.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/i2c/algos/i2c-algo-bit.c
+++ b/drivers/i2c/algos/i2c-algo-bit.c
@@ -103,8 +103,14 @@ static int sclhi(struct i2c_algo_bit_dat
* chips may hold it low ("clock stretching") while they
* are processing data internally.
*/
- if (time_after(jiffies, start + adap->timeout))
+ if (time_after(jiffies, start + adap->timeout)) {
+ /* Test one last time, as we may have been preempted
+ * between last check and timeout test.
+ */
+ if (getscl(adap))
+ break;
return -ETIMEDOUT;
+ }
cond_resched();
}
#ifdef DEBUG
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/i2c-algo-bit-fix-spurious-scl-timeouts-under-heavy-load.patch
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