[Bugfix] unregister_trace_probe needs to be called under mutex

[Bugfix] unregister_trace_probe needs to be called under mutex

[Srikar Dronamraju]

Comment in unregister_trace_probe() says probe_lock will be held
when it gets called. However there is a case where it might called
without the probe_lock being held. Also since we are traversing the
probe_list and deleting an element from the probe_list, probe_lock
should be held.

This was first pointed in uprobes traceevent review by Frederic
Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)

This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 4f11a56..67670cd 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
 			pr_info("Delete command needs an event name.\n");
 			return -EINVAL;
 		}
+		mutex_lock(&probe_lock);
 		tp = find_probe_event(event, group);
 		if (!tp) {
+			mutex_unlock(&probe_lock);
 			pr_info("Event %s/%s doesn't exist.\n", group, event);
 			return -ENOENT;
 		}
 		/* delete an event */
 		unregister_trace_probe(tp);
 		free_trace_probe(tp);
+		mutex_unlock(&probe_lock);
 		return 0;
 	}
 

Re: [Bugfix] unregister_trace_probe needs to be called under mutex

[Peter Zijlstra]

On Wed, 2010-06-30 at 14:15 +0530, Srikar Dronamraju wrote:
> Comment in unregister_trace_probe() says probe_lock will be held
> when it gets called. However there is a case where it might called
> without the probe_lock being held. Also since we are traversing the
> probe_list and deleting an element from the probe_list, probe_lock
> should be held.
> 
> This was first pointed in uprobes traceevent review by Frederic
> Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)
> 
> This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip
> 
> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 4f11a56..67670cd 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
>  			pr_info("Delete command needs an event name.\n");
>  			return -EINVAL;
>  		}
> +		mutex_lock(&probe_lock);
>  		tp = find_probe_event(event, group);
>  		if (!tp) {
> +			mutex_unlock(&probe_lock);
>  			pr_info("Event %s/%s doesn't exist.\n", group, event);
>  			return -ENOENT;
>  		}
>  		/* delete an event */
>  		unregister_trace_probe(tp);
>  		free_trace_probe(tp);
> +		mutex_unlock(&probe_lock);
>  		return 0;
>  	}

Shouldn't all that go through steven's ->reg() interface?

Re: [Bugfix] unregister_trace_probe needs to be called under mutex

[Srikar Dronamraju]

> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 4f11a56..67670cd 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
> >  			pr_info("Delete command needs an event name.\n");
> >  			return -EINVAL;
> >  		}
> > +		mutex_lock(&probe_lock);
> >  		tp = find_probe_event(event, group);
> >  		if (!tp) {
> > +			mutex_unlock(&probe_lock);
> >  			pr_info("Event %s/%s doesn't exist.\n", group, event);
> >  			return -ENOENT;
> >  		}
> >  		/* delete an event */
> >  		unregister_trace_probe(tp);
> >  		free_trace_probe(tp);
> > +		mutex_unlock(&probe_lock);
> >  		return 0;
> >  	}
> 
> Shouldn't all that go through steven's ->reg() interface?

Currently the ->reg() interface does a enable/disable of the
probe_events. Infact the reg callback gets set in
register_trace_probe() function which inturn gets called from the
create_trace_probe().

Do we have plans to move probe_events creation to ->reg()
interface?

--
Regards
Srikar

Re: [Bugfix] unregister_trace_probe needs to be called under mutex

[Steven Rostedt]

On Wed, 2010-06-30 at 11:44 +0200, Peter Zijlstra wrote:
> On Wed, 2010-06-30 at 14:15 +0530, Srikar Dronamraju wrote:
> > Comment in unregister_trace_probe() says probe_lock will be held
> > when it gets called. However there is a case where it might called
> > without the probe_lock being held. Also since we are traversing the
> > probe_list and deleting an element from the probe_list, probe_lock
> > should be held.
> > 
> > This was first pointed in uprobes traceevent review by Frederic
> > Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)
> > 
> > This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip

Acked-by: Steven Rostedt <rostedt@goodmis.org>

> > 
> > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> > ---
> > 
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 4f11a56..67670cd 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
> >  			pr_info("Delete command needs an event name.\n");
> >  			return -EINVAL;
> >  		}
> > +		mutex_lock(&probe_lock);
> >  		tp = find_probe_event(event, group);
> >  		if (!tp) {
> > +			mutex_unlock(&probe_lock);
> >  			pr_info("Event %s/%s doesn't exist.\n", group, event);
> >  			return -ENOENT;
> >  		}
> >  		/* delete an event */
> >  		unregister_trace_probe(tp);
> >  		free_trace_probe(tp);
> > +		mutex_unlock(&probe_lock);
> >  		return 0;
> >  	}
> 
> Shouldn't all that go through steven's ->reg() interface?

Nah, this is specific to the kprobe code. Has really nothing to do with
the ->reg() interface.

-- Steve

Re: [Bugfix] unregister_trace_probe needs to be called under mutex

[Masami Hiramatsu]

Srikar Dronamraju wrote:
> Comment in unregister_trace_probe() says probe_lock will be held
> when it gets called. However there is a case where it might called
> without the probe_lock being held. Also since we are traversing the
> probe_list and deleting an element from the probe_list, probe_lock
> should be held.
> 
> This was first pointed in uprobes traceevent review by Frederic
> Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)
> 
> This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip
> 
> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Ah, right! That's definately needed.

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you!


> ---
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 4f11a56..67670cd 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
>  			pr_info("Delete command needs an event name.\n");
>  			return -EINVAL;
>  		}
> +		mutex_lock(&probe_lock);
>  		tp = find_probe_event(event, group);
>  		if (!tp) {
> +			mutex_unlock(&probe_lock);
>  			pr_info("Event %s/%s doesn't exist.\n", group, event);
>  			return -ENOENT;
>  		}
>  		/* delete an event */
>  		unregister_trace_probe(tp);
>  		free_trace_probe(tp);
> +		mutex_unlock(&probe_lock);
>  		return 0;
>  	}
>  

Re: [Bugfix] unregister_trace_probe needs to be called under mutex

[Srikar Dronamraju]

Ingo, 

Any particular reason to not pick this patch?

Steven Rostedt and Masami Hiramatsu agree that this patch needs to be
pushed in.

--
Thanks and Regards
Srikar

> Srikar Dronamraju wrote:
> > Comment in unregister_trace_probe() says probe_lock will be held
> > when it gets called. However there is a case where it might called
> > without the probe_lock being held. Also since we are traversing the
> > probe_list and deleting an element from the probe_list, probe_lock
> > should be held.
> > 
> > This was first pointed in uprobes traceevent review by Frederic
> > Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)
> > 
> > This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip
> > 
> > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> 
> Ah, right! That's definately needed.
> 
> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> 
> Thank you!
> 
> 
> > ---
> > 
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 4f11a56..67670cd 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
> >  			pr_info("Delete command needs an event name.\n");
> >  			return -EINVAL;
> >  		}
> > +		mutex_lock(&probe_lock);
> >  		tp = find_probe_event(event, group);
> >  		if (!tp) {
> > +			mutex_unlock(&probe_lock);
> >  			pr_info("Event %s/%s doesn't exist.\n", group, event);
> >  			return -ENOENT;
> >  		}
> >  		/* delete an event */
> >  		unregister_trace_probe(tp);
> >  		free_trace_probe(tp);
> > +		mutex_unlock(&probe_lock);
> >  		return 0;
> >  	}
> >  
> 

[tip:perf/core] tracing/kprobes: unregister_trace_probe needs to be called under mutex

[tip-bot for Srikar Dronamraju]

Commit-ID:  9da79ab83ee33ddc1fdd0858fd3d70925a1bde99
Gitweb:     http://git.kernel.org/tip/9da79ab83ee33ddc1fdd0858fd3d70925a1bde99
Author:     Srikar Dronamraju <srikar@linux.vnet.ibm.com>
AuthorDate: Wed, 30 Jun 2010 14:15:48 +0530
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 4 Aug 2010 12:41:23 -0300

tracing/kprobes: unregister_trace_probe needs to be called under mutex

Comment in unregister_trace_probe() says probe_lock will be held when it
gets called. However there is a case where it might called without the
probe_lock being held. Also since we are traversing the probe_list and
deleting an element from the probe_list, probe_lock should be held.

This was first pointed in uprobes traceevent review by Frederic
Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100630084548.GA10325@linux.vnet.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 kernel/trace/trace_kprobe.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 1b79d1c..8b27c98 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -925,14 +925,17 @@ static int create_trace_probe(int argc, char **argv)
 			pr_info("Delete command needs an event name.\n");
 			return -EINVAL;
 		}
+		mutex_lock(&probe_lock);
 		tp = find_probe_event(event, group);
 		if (!tp) {
+			mutex_unlock(&probe_lock);
 			pr_info("Event %s/%s doesn't exist.\n", group, event);
 			return -ENOENT;
 		}
 		/* delete an event */
 		unregister_trace_probe(tp);
 		free_trace_probe(tp);
+		mutex_unlock(&probe_lock);
 		return 0;
 	}