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Subject[PATCH] FMC: fix locking in sample chardev driver
The fmc-chardev module was over-locking, by calling misc
register/unregister while holding its spinlock. This reported a
"scheduling while atomic" error.

Since the misc driver already serializes operations internally, this
commit downgrades the fmc-chardev lock to just cover its own list.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
---
drivers/fmc/fmc-chardev.c | 9 ++++-----
1 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/fmc/fmc-chardev.c b/drivers/fmc/fmc-chardev.c
index cc031db..ace6ef2 100644
--- a/drivers/fmc/fmc-chardev.c
+++ b/drivers/fmc/fmc-chardev.c
@@ -143,18 +143,17 @@ static int fc_probe(struct fmc_device *fmc)
fc->misc.fops = &fc_fops;
fc->misc.name = kstrdup(dev_name(&fmc->dev), GFP_KERNEL);

- spin_lock(&fc_lock);
ret = misc_register(&fc->misc);
if (ret < 0)
- goto err_unlock;
+ goto out;
+ spin_lock(&fc_lock);
list_add(&fc->list, &fc_devices);
spin_unlock(&fc_lock);
dev_info(&fc->fmc->dev, "Created misc device \"%s\"\n",
fc->misc.name);
return 0;

-err_unlock:
- spin_unlock(&fc_lock);
+out:
kfree(fc->misc.name);
kfree(fc);
return ret;
@@ -174,10 +173,10 @@ static int fc_remove(struct fmc_device *fmc)

spin_lock(&fc_lock);
list_del(&fc->list);
+ spin_unlock(&fc_lock);
misc_deregister(&fc->misc);
kfree(fc->misc.name);
kfree(fc);
- spin_unlock(&fc_lock);

return 0;
}
--
1.7.7.2

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