search for: c591d7e

If we read hwrng by long-running dd process, it takes too much cpu time. When we check hwrng attributes from sysfs by cat, it gets stuck. The problem can only be reproduced with non-smp guest with slow backend. This patchset changed hwrng core to always delay 10 jiffies, cat process have chance to execute protected code, the problem is resolved. Thanks. Amos Kong (2): virtio-rng cleanup: move

If we read hwrng by long-running dd process, it takes too much cpu time. When we check hwrng attributes from sysfs by cat, it gets stuck. The problem can only be reproduced with non-smp guest with slow backend. This patchset changed hwrng core to always delay 10 jiffies, cat process have chance to execute protected code, the problem is resolved. Thanks. Amos Kong (2): virtio-rng cleanup: move

...Amos Kong <akong at redhat.com> > > > --- > > > drivers/char/hw_random/core.c | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > > index c591d7e..b5d1b6f 100644 > > > --- a/drivers/char/hw_random/core.c > > > +++ b/drivers/char/hw_random/core.c > > > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > > > > > mutex_unlock(&rng_mutex); > > >...

...Amos Kong <akong at redhat.com> > > > --- > > > drivers/char/hw_random/core.c | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > > index c591d7e..b5d1b6f 100644 > > > --- a/drivers/char/hw_random/core.c > > > +++ b/drivers/char/hw_random/core.c > > > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > > > > > mutex_unlock(&rng_mutex); > > >...

...so works, but 10 jiffies is safer. > > Signed-off-by: Amos Kong <akong at redhat.com> > --- > drivers/char/hw_random/core.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > index c591d7e..b5d1b6f 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > mutex_unlock(&rng_mutex); > > - if (need_resched()) > - schedule_timeout_inter...

...so works, but 10 jiffies is safer. > > Signed-off-by: Amos Kong <akong at redhat.com> > --- > drivers/char/hw_random/core.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > index c591d7e..b5d1b6f 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > mutex_unlock(&rng_mutex); > > - if (need_resched()) > - schedule_timeout_inter...

If we read hwrng by long-running dd process, it takes too much cpu time and almost hold the mutex lock. When we check hwrng attributes from sysfs by cat, it gets stuck in waiting the lock releaseing. The problem can only be reproduced with non-smp guest with slow backend. This patchset resolves the issue by changing rng_dev_read() to always schedule 10 jiffies after release mutex lock, then cat

If we read hwrng by long-running dd process, it takes too much cpu time and almost hold the mutex lock. When we check hwrng attributes from sysfs by cat, it gets stuck in waiting the lock releaseing. The problem can only be reproduced with non-smp guest with slow backend. This patchset resolves the issue by changing rng_dev_read() to always schedule 10 jiffies after release mutex lock, then cat

2014-09-14 10:25+0800, Amos Kong: > On Sun, Sep 14, 2014 at 09:12:08AM +0800, Amos Kong wrote: > > ... > > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > > > > index c591d7e..b5d1b6f 100644 > > > > > --- a/drivers/char/hw_random/core.c > > > > > +++ b/drivers/char/hw_random/core.c > > > > > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > > > > > > > > >...

2014-09-14 10:25+0800, Amos Kong: > On Sun, Sep 14, 2014 at 09:12:08AM +0800, Amos Kong wrote: > > ... > > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > > > > index c591d7e..b5d1b6f 100644 > > > > > --- a/drivers/char/hw_random/core.c > > > > > +++ b/drivers/char/hw_random/core.c > > > > > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > > > > > > > > >...

...ed, just a cleanup. > > Signed-off-by: Amos Kong <akong at 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 aa30a25..c591d7e 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -270,8 +270,8 @@ static ssize_t hwrng_attr_current_show(struct device *dev, > return -ERESTARTSYS; > if (current_rng) > name = current_rng->name; > - ret = snprintf(buf, PAGE_SIZE...

...ed, just a cleanup. > > Signed-off-by: Amos Kong <akong at 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 aa30a25..c591d7e 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -270,8 +270,8 @@ static ssize_t hwrng_attr_current_show(struct device *dev, > return -ERESTARTSYS; > if (current_rng) > name = current_rng->name; > - ret = snprintf(buf, PAGE_SIZE...

...n't save too much cpu time as expected, just a cleanup. Signed-off-by: Amos Kong <akong at 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 aa30a25..c591d7e 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -270,8 +270,8 @@ static ssize_t hwrng_attr_current_show(struct device *dev, return -ERESTARTSYS; if (current_rng) name = current_rng->name; - ret = snprintf(buf, PAGE_SIZE, "%s\n", name); mutex_...

...te protected code. Delaying 1 jiffy also works, but 10 jiffies is safer. Signed-off-by: Amos Kong <akong at redhat.com> --- drivers/char/hw_random/core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index c591d7e..b5d1b6f 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, mutex_unlock(&rng_mutex); - if (need_resched()) - schedule_timeout_interruptible(1); + schedule_timeout_interru...

...> > > Signed-off-by: Amos Kong <akong at redhat.com> > > --- > > drivers/char/hw_random/core.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > index c591d7e..b5d1b6f 100644 > > --- a/drivers/char/hw_random/core.c > > +++ b/drivers/char/hw_random/core.c > > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > > > mutex_unlock(&rng_mutex); > > > > - if (need_resched...

...<amit.shah at redhat.com> > > Signed-off-by: Amos Kong <akong at redhat.com> > --- > drivers/char/hw_random/core.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > index c591d7e..b5d1b6f 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > mutex_unlock(&rng_mutex); > > - if (need_resched()) > - schedule_timeout_inter...

...n't save too much cpu time as expected, just a cleanup. Signed-off-by: Amos Kong <akong at 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 aa30a25..c591d7e 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -270,8 +270,8 @@ static ssize_t hwrng_attr_current_show(struct device *dev, return -ERESTARTSYS; if (current_rng) name = current_rng->name; - ret = snprintf(buf, PAGE_SIZE, "%s\n", name); mutex_...

On Sun, Sep 14, 2014 at 09:12:08AM +0800, Amos Kong wrote: ... > > > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > > > > index c591d7e..b5d1b6f 100644 > > > > --- a/drivers/char/hw_random/core.c > > > > +++ b/drivers/char/hw_random/core.c > > > > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > > > > > > > mutex_unlock(&rng...

...other tasks can have chance to hold the lock and execute protected code. Signed-off-by: Amos Kong <akong at redhat.com> --- drivers/char/hw_random/core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index c591d7e..263a370 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, mutex_unlock(&rng_mutex); - if (need_resched()) - schedule_timeout_interruptible(1); + schedule_timeout_interru...

...<amit.shah at redhat.com> > > Signed-off-by: Amos Kong <akong at redhat.com> > --- > drivers/char/hw_random/core.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > index c591d7e..b5d1b6f 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, > > mutex_unlock(&rng_mutex); > > - if (need_resched()) > - schedule_timeout_inter...