| From 26613a2b67477b2f6a5613ef7170a2cde4e372e3 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 29 Jun 2020 23:45:56 -0400 |
| Subject: tracing: Move pipe reference to trace array instead of current_tracer |
| |
| 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 |
| -- |
| 2.25.1 |
| |