search for: current_rng

From: Rusty Russell <rusty at rustcorp.com.au> 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 th...

From: Rusty Russell <rusty at rustcorp.com.au> 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 th...

On Thu, Sep 18, 2014 at 08:37:44PM +0800, Amos Kong wrote: > From: Rusty Russell <rusty at rustcorp.com.au> > > 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...

On Thu, Sep 18, 2014 at 08:37:44PM +0800, Amos Kong wrote: > From: Rusty Russell <rusty at rustcorp.com.au> > > 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...

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 th...

From: Rusty Russell <rusty at rustcorp.com.au> 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 th...

Amos Kong <akong at redhat.com> writes: > We got a warning in boot stage when above set_current_rng() is executed, > it can be fixed by init rng->ref in hwrng_init(). > > > @@ -166,6 +169,8 @@ static inline int hwrng_init(struct hwrng *rng) > if (current_quality > 0 && !hwrng_fill) > start_khwrngd(); > > + kref_init(&rng-&g...

Amos Kong <akong at redhat.com> writes: > We got a warning in boot stage when above set_current_rng() is executed, > it can be fixed by init rng->ref in hwrng_init(). > > > @@ -166,6 +169,8 @@ static inline int hwrng_init(struct hwrng *rng) > if (current_quality > 0 && !hwrng_fill) > start_khwrngd(); > > + kref_init(&rng-&g...

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My original was pain, Rusty posted a real fix. This patchset fixed two issue in v1, and tested by my 6+ cases. | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: |

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My original was pain, Rusty posted a real fix. This patchset fixed two issue in v1, and tested by my 6+ cases. | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: |

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My hotplug tests: | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: | guest) # dd if=/dev/random of=/dev/null & | hotunplug rng device from qemu monitor | | test

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My hotplug tests: | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: | guest) # dd if=/dev/random of=/dev/null & | hotunplug rng device from qemu monitor | | test

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My hotplug tests: | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: | guest) # dd if=/dev/random of=/dev/null & | hotunplug rng device from qemu monitor | | test

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My hotplug tests: | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: | guest) # dd if=/dev/random of=/dev/null & | hotunplug rng device from qemu monitor | | test

...+++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index aa30a25c8d49..b1b6042ad85c 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -53,7 +53,10 @@ static struct hwrng *current_rng; static struct task_struct *hwrng_fill; static LIST_HEAD(rng_list); +/* Protects rng_list and current_rng */ static DEFINE_MUTEX(rng_mutex); +/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */ +static DEFINE_MUTEX(reading_mutex); static int data_avail; static u8 *rng_buf...

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My hotplug tests: | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: | guest) # dd if=/dev/random of=/dev/null & | hotunplug rng device from qemu monitor | | test

When I hotunplug a busy virtio-rng device or try to access hwrng attributes in non-smp guest, it gets stuck. My hotplug tests: | test 0: | hotunplug rng device from qemu monitor | | test 1: | guest) # dd if=/dev/hwrng of=/dev/null & | hotunplug rng device from qemu monitor | | test 2: | guest) # dd if=/dev/random of=/dev/null & | hotunplug rng device from qemu monitor | | test

Amos Kong <akong at redhat.com> writes: > I started a QEMU (non-smp) guest with one virtio-rng device, and read > random data from /dev/hwrng by dd: > > # dd if=/dev/hwrng of=/dev/null & > > In the same time, if I check hwrng attributes from sysfs by cat: > > # cat /sys/class/misc/hw_random/rng_* > > The cat process always gets stuck with slow backend (5

Amos Kong <akong at redhat.com> writes: > I started a QEMU (non-smp) guest with one virtio-rng device, and read > random data from /dev/hwrng by dd: > > # dd if=/dev/hwrng of=/dev/null & > > In the same time, if I check hwrng attributes from sysfs by cat: > > # cat /sys/class/misc/hw_random/rng_* > > The cat process always gets stuck with slow backend (5

...om/show_bug.cgi?id=1127062 steps: - Read random data by 'dd if=/dev/hwrng of=/dev/null' in guest - check sysfs files in the same time, 'cat /sys/class/misc/hw_random/rng_*' Result: cat process will get stuck, it will return if we kill dd process. We have some static variables (eg, current_rng, data_avail, etc) in hw_random/core.c, they are protected by rng_mutex. I try to workaround this issue by undelay(100) after mutex_unlock() in rng_dev_read(). This gives chance for hwrng_attr_*_show() to get mutex. This patch also contains some cleanup, moving some code out of mutex protection. D...