diff options
| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-02-05 09:20:32 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-02-11 04:35:28 -0800 |
| commit | c8e9dafe668d9c50e1b1287ac2375497d747f367 (patch) | |
| tree | 98299bbb745531c6b2bc794bc20e7e39f5009f0e | |
| parent | 6a652ed941aa3e31a645c4074ef2a80b2535f5b9 (diff) | |
ftrace: Protect ftrace_graph_hash with ftrace_sync
[ Upstream commit 54a16ff6f2e50775145b210bcd94d62c3c2af117 ]
As function_graph tracer can run when RCU is not "watching", it can not be
protected by synchronize_rcu() it requires running a task on each CPU before
it can be freed. Calling schedule_on_each_cpu(ftrace_sync) needs to be used.
Link: https://lore.kernel.org/r/20200205131110.GT2935@paulmck-ThinkPad-P72
Cc: stable@vger.kernel.org
Fixes: b9b0c831bed26 ("ftrace: Convert graph filter to use hash tables")
Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/trace/ftrace.c | 11 | ||||
| -rw-r--r-- | kernel/trace/trace.h | 2 |
2 files changed, 11 insertions, 2 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index d297a8bdc681..407d8bf4ed93 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5378,8 +5378,15 @@ ftrace_graph_release(struct inode *inode, struct file *file) mutex_unlock(&graph_lock); - /* Wait till all users are no longer using the old hash */ - synchronize_rcu(); + /* + * We need to do a hard force of sched synchronization. + * This is because we use preempt_disable() to do RCU, but + * the function tracers can be called where RCU is not watching + * (like before user_exit()). We can not rely on the RCU + * infrastructure to do the synchronization, thus we must do it + * ourselves. + */ + schedule_on_each_cpu(ftrace_sync); free_ftrace_hash(old_hash); } diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 08647723cfab..a3c29d5fcc61 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -947,6 +947,7 @@ static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace) * Have to open code "rcu_dereference_sched()" because the * function graph tracer can be called when RCU is not * "watching". + * Protected with schedule_on_each_cpu(ftrace_sync) */ hash = rcu_dereference_protected(ftrace_graph_hash, !preemptible()); @@ -999,6 +1000,7 @@ static inline int ftrace_graph_notrace_addr(unsigned long addr) * Have to open code "rcu_dereference_sched()" because the * function graph tracer can be called when RCU is not * "watching". + * Protected with schedule_on_each_cpu(ftrace_sync) */ notrace_hash = rcu_dereference_protected(ftrace_graph_notrace_hash, !preemptible()); |