Re: [PATCH v2] hw_random: core, sleep interruptible in read

[Herbert Xu]

On Fri, Nov 27, 2015 at 04:50:43PM +0100, Jiri Slaby wrote:
> hwrng kthread can be waiting via hwrng_fillfn for some data from a rng
> like virtio-rng:
> hwrng           D ffff880093e17798     0   382      2 0x00000000
> ...
> Call Trace:
>  [<ffffffff817339c6>] wait_for_completion_killable+0x96/0x210
>  [<ffffffffa00aa1b7>] virtio_read+0x57/0xf0 [virtio_rng]
>  [<ffffffff814f4a35>] hwrng_fillfn+0x75/0x130
>  [<ffffffff810aa243>] kthread+0xf3/0x110
> 
> And when some user program tries to read the /dev node in this state,
> we get:
> rngd            D ffff880093e17798     0   762      1 0x00000004
> ...
> Call Trace:
>  [<ffffffff817351ac>] mutex_lock_nested+0x15c/0x3e0
>  [<ffffffff814f478e>] rng_dev_read+0x6e/0x240
>  [<ffffffff81231958>] __vfs_read+0x28/0xe0
>  [<ffffffff81232393>] vfs_read+0x83/0x130
> 
> And this is indeed unkillable. So use mutex_lock_interruptible
> instead of mutex_lock in rng_dev_read and exit immediatelly when
> interrupted. And possibly return already read data, if any (as POSIX
> allows).
> 
> v2: use ERESTARTSYS instead of EINTR
> 
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Cc: Matt Mackall <mpm@xxxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: <linux-crypto@xxxxxxxxxxxxxxx>

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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