Messages in this thread Patch in this message | | | Date | Fri, 16 Mar 2012 16:38:48 -0700 | From | Greg KH <> | Subject | [ 38/41] i2c-algo-bit: Fix spurious SCL timeouts under heavy load |
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3.2-stable review patch. If anyone has any objections, please let me know.
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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
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