From: Steven Rostedt (VMware) rostedt@goodmis.org
[ Upstream commit 7ef282e05132d56b6f6b71e3873f317664bea78b ]
If a process has the trace_pipe open on a trace_array, the current tracer for that trace array should not be changed. This was original enforced by a global lock, but when instances were introduced, it was moved to the current_trace. But this structure is shared by all instances, and a trace_pipe is for a single instance. There's no reason that a process that has trace_pipe open on one instance should prevent another instance from changing its current tracer. Move the reference counter to the trace_array instead.
This is marked as "Fixes" but is more of a clean up than a true fix. Backport if you want, but its not critical.
Fixes: cf6ab6d9143b1 ("tracing: Add ref count to tracer for when they are being read by pipe") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace.c | 12 ++++++------ kernel/trace/trace.h | 2 +- 2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 29615f15a820b..5c56c1e2f2735 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5885,7 +5885,7 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf) }
/* If trace pipe files are being read, we can't change the tracer */ - if (tr->current_trace->ref) { + if (tr->trace_ref) { ret = -EBUSY; goto out; } @@ -6101,7 +6101,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
nonseekable_open(inode, filp);
- tr->current_trace->ref++; + tr->trace_ref++; out: mutex_unlock(&trace_types_lock); return ret; @@ -6120,7 +6120,7 @@ static int tracing_release_pipe(struct inode *inode, struct file *file)
mutex_lock(&trace_types_lock);
- tr->current_trace->ref--; + tr->trace_ref--;
if (iter->trace->pipe_close) iter->trace->pipe_close(iter); @@ -7429,7 +7429,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
filp->private_data = info;
- tr->current_trace->ref++; + tr->trace_ref++;
mutex_unlock(&trace_types_lock);
@@ -7530,7 +7530,7 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
mutex_lock(&trace_types_lock);
- iter->tr->current_trace->ref--; + iter->tr->trace_ref--;
__trace_array_put(iter->tr);
@@ -8752,7 +8752,7 @@ static int __remove_instance(struct trace_array *tr) int i;
/* Reference counter for a newly created trace array = 1. */ - if (tr->ref > 1 || (tr->current_trace && tr->current_trace->ref)) + if (tr->ref > 1 || (tr->current_trace && tr->trace_ref)) return -EBUSY;
list_del(&tr->list); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 7fb2f4c1bc498..09298ce5f805b 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -356,6 +356,7 @@ struct trace_array { struct trace_event_file *trace_marker_file; cpumask_var_t tracing_cpumask; /* only trace on set CPUs */ int ref; + int trace_ref; #ifdef CONFIG_FUNCTION_TRACER struct ftrace_ops *ops; struct trace_pid_list __rcu *function_pids; @@ -547,7 +548,6 @@ struct tracer { struct tracer *next; struct tracer_flags *flags; int enabled; - int ref; bool print_max; bool allow_instances; #ifdef CONFIG_TRACER_MAX_TRACE