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Subject[PATCH v4 2/6] hw_random: move some code out mutex_lock for avoiding underlying deadlock
Date
In next patch, we use reference counting for each struct hwrng,
changing reference count also needs to take mutex_lock. Before
releasing the lock, if we try to stop a kthread that waits to
take the lock to reduce the referencing count, deadlock will
occur.

Signed-off-by: Amos Kong <akong@redhat.com>
---
drivers/char/hw_random/core.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index b1b6042..a0905c8 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -474,12 +474,12 @@ void hwrng_unregister(struct hwrng *rng)
}
}
if (list_empty(&rng_list)) {
+ mutex_unlock(&rng_mutex);
unregister_miscdev();
if (hwrng_fill)
kthread_stop(hwrng_fill);
- }
-
- mutex_unlock(&rng_mutex);
+ } else
+ mutex_unlock(&rng_mutex);
}
EXPORT_SYMBOL_GPL(hwrng_unregister);

--
1.9.3


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