lkml.org 
[lkml]   [2012]   [Mar]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[ 38/41] i2c-algo-bit: Fix spurious SCL timeouts under heavy load
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ville Syrjala <syrjala@sci.fi>

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 <syrjala@sci.fi>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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



\
 
 \ /
  Last update: 2012-03-17 00:45    [W:0.861 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site