hwrng: use reference counts on each struct hwrng.

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current_rng holds one reference, and we bump it every time we want
to do a read from it.

This means we only hold the rng_mutex to grab or drop a reference,
so accessing /sys/devices/virtual/misc/hw_random/rng_current doesn't
block on read of /dev/hwrng.

Using a kref is overkill (we're always under the rng_mutex), but
a standard pattern.

This also solves the problem that the hwrng_fillfn thread was
accessing current_rng without a lock, which could change (eg. to NULL)
underneath it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

...

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Rusty Russell 2014-12-08 16:50:37 +08:00 • committed by Herbert Xu

parent 1dacb395d6

commit 3a2c0ba5ad

2 changed files with 94 additions and 43 deletions

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135

drivers/char/hw_random/core.c

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2

include/linux/hw_random.h

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