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Groups > linux.kernel > #1278421 > unrolled thread
| Started by | Jiri Slaby <jslaby@suse.cz> |
|---|---|
| First post | 2015-11-26 21:00 +0100 |
| Last post | 2015-11-27 17:00 +0100 |
| Articles | 4 — 2 participants |
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[PATCH] hw_random: core, sleep interruptible in read Jiri Slaby <jslaby@suse.cz> - 2015-11-26 21:00 +0100
Re: [PATCH] hw_random: core, sleep interruptible in read Herbert Xu <herbert@gondor.apana.org.au> - 2015-11-27 14:10 +0100
Re: [PATCH] hw_random: core, sleep interruptible in read Jiri Slaby <jslaby@suse.cz> - 2015-11-27 16:50 +0100
[PATCH v2] hw_random: core, sleep interruptible in read Jiri Slaby <jslaby@suse.cz> - 2015-11-27 17:00 +0100
| From | Jiri Slaby <jslaby@suse.cz> |
|---|---|
| Date | 2015-11-26 21:00 +0100 |
| Subject | [PATCH] hw_random: core, sleep interruptible in read |
| Message-ID | <qzaRY-16M-5@gated-at.bofh.it> |
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).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: <linux-crypto@vger.kernel.org>
---
drivers/char/hw_random/core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index a064237ff362..f003df162e09 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -238,7 +238,10 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
goto out;
}
- mutex_lock(&reading_mutex);
+ if (mutex_lock_interruptible(&reading_mutex)) {
+ err = -EINTR;
+ goto out_put;
+ }
if (!data_avail) {
bytes_read = rng_get_data(rng, rng_buffer,
rng_buffer_size(),
@@ -288,6 +291,7 @@ out:
out_unlock_reading:
mutex_unlock(&reading_mutex);
+out_put:
put_rng(rng);
goto out;
}
--
2.6.3
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| From | Herbert Xu <herbert@gondor.apana.org.au> |
|---|---|
| Date | 2015-11-27 14:10 +0100 |
| Message-ID | <qzqWK-3hn-39@gated-at.bofh.it> |
| In reply to | #1278421 |
On Thu, Nov 26, 2015 at 08:56:29PM +0100, Jiri Slaby wrote:
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index a064237ff362..f003df162e09 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -238,7 +238,10 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
> goto out;
> }
>
> - mutex_lock(&reading_mutex);
> + if (mutex_lock_interruptible(&reading_mutex)) {
> + err = -EINTR;
Shouldn't this be ERESTARTSYS?
Thanks,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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| From | Jiri Slaby <jslaby@suse.cz> |
|---|---|
| Date | 2015-11-27 16:50 +0100 |
| Message-ID | <qztrB-4LC-27@gated-at.bofh.it> |
| In reply to | #1278797 |
On 11/27/2015, 02:06 PM, Herbert Xu wrote:
> On Thu, Nov 26, 2015 at 08:56:29PM +0100, Jiri Slaby wrote:
>>
>> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
>> index a064237ff362..f003df162e09 100644
>> --- a/drivers/char/hw_random/core.c
>> +++ b/drivers/char/hw_random/core.c
>> @@ -238,7 +238,10 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
>> goto out;
>> }
>>
>> - mutex_lock(&reading_mutex);
>> + if (mutex_lock_interruptible(&reading_mutex)) {
>> + err = -EINTR;
>
> Shouldn't this be ERESTARTSYS?
Yes, it actually can, given the retval is returned only if no data were
read yet.
thanks,
--
js
suse labs
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| From | Jiri Slaby <jslaby@suse.cz> |
|---|---|
| Date | 2015-11-27 17:00 +0100 |
| Subject | [PATCH v2] hw_random: core, sleep interruptible in read |
| Message-ID | <qztBg-4Pa-17@gated-at.bofh.it> |
| In reply to | #1278797 |
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@suse.cz>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: <linux-crypto@vger.kernel.org>
---
drivers/char/hw_random/core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index a064237ff362..ca5a5325eb6f 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -238,7 +238,10 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
goto out;
}
- mutex_lock(&reading_mutex);
+ if (mutex_lock_interruptible(&reading_mutex)) {
+ err = -ERESTARTSYS;
+ goto out_put;
+ }
if (!data_avail) {
bytes_read = rng_get_data(rng, rng_buffer,
rng_buffer_size(),
@@ -288,6 +291,7 @@ out:
out_unlock_reading:
mutex_unlock(&reading_mutex);
+out_put:
put_rng(rng);
goto out;
}
--
2.6.3
--
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