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tracing: Move pipe reference to trace array instead of current_tracer 

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: cf6ab6d914 ("tracing: Add ref count to tracer for when they are being read by pipe")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-06-29 23:45:56 -04:00
parent e6bc5b3f42
commit 7ef282e051
2 changed files with 7 additions and 7 deletions
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12
kernel/trace/trace.c
View File

@ -5891,7 +5891,7 @@ 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;
}
@ -6107,7 +6107,7 @@ 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;
@ -6126,7 +6126,7 @@ 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);
@ -7428,7 +7428,7 @@ 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);
@ -7529,7 +7529,7 @@ 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);
@ -8737,7 +8737,7 @@ 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);

2
kernel/trace/trace.h
View File

@ -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