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of: fix race when matching drivers

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If two drivers are probing devices at the same time, both will write
their match table result to the dev->of_match cache at the same time.

Only write the result if the device matches.

In a thread titled "SBus devices sometimes detected, sometimes not",
Meelis reported his SBus hme was not detected about 50% of the time.
From the debug suggested by Grant it was obvious another driver matched
some devices between the call to match the hme and the hme discovery
failling.

Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Milton Miller <miltonm@bga.com>
[grant.likely: modified to only call of_match_device() once]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Milton Miller 2011-05-18 10:27:39 -05:00 committed by Grant Likely
parent 2e9521fd65
commit 01294d8262
1 changed files with 6 additions and 2 deletions
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8
include/linux/of_device.h
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@ -21,8 +21,12 @@ extern void of_device_make_bus_id(struct device *dev);
static inline int of_driver_match_device(struct device *dev,
const struct device_driver *drv)
{
dev->of_match = of_match_device(drv->of_match_table, dev);
return dev->of_match != NULL;
const struct of_device_id *match;
match = of_match_device(drv->of_match_table, dev);
if (match)
dev->of_match = match;
return match != NULL;
}
extern struct platform_device *of_dev_get(struct platform_device *dev);