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tracing: Add ref count to tracer for when they are being read by pipe

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When one of the trace pipe files are being read (by either the trace_pipe
or trace_pipe_raw), do not allow the current_trace to change. By adding
a ref count that is incremented when the pipe files are opened, will
prevent the current_trace from being changed.

This will allow for the removal of the global trace_types_lock from
reading the pipe buffers (which is currently a bottle neck).

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-12-15 20:13:31 -05:00 committed by Steven Rostedt
parent 97bf6af1f9
commit cf6ab6d914
2 changed files with 16 additions and 1 deletions
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16
kernel/trace/trace.c
View File

@ -4140,6 +4140,12 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
goto out;
}
/* If trace pipe files are being read, we can't change the tracer */
if (tr->current_trace->ref) {
ret = -EBUSY;
goto out;
}
trace_branch_disable();
tr->current_trace->enabled--;
@ -4363,6 +4369,8 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
iter->trace->pipe_open(iter);
nonseekable_open(inode, filp);
tr->current_trace->ref++;
out:
mutex_unlock(&trace_types_lock);
return ret;
@ -4382,6 +4390,8 @@ static int tracing_release_pipe(struct inode *inode, struct file *file)
mutex_lock(&trace_types_lock);
tr->current_trace->ref--;
if (iter->trace->pipe_close)
iter->trace->pipe_close(iter);
@ -5331,6 +5341,8 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
filp->private_data = info;
tr->current_trace->ref++;
mutex_unlock(&trace_types_lock);
ret = nonseekable_open(inode, filp);
@ -5437,6 +5449,8 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
mutex_lock(&trace_types_lock);
iter->tr->current_trace->ref--;
__trace_array_put(iter->tr);
if (info->spare)
@ -6416,7 +6430,7 @@ static int instance_delete(const char *name)
goto out_unlock;
ret = -EBUSY;
if (tr->ref)
if (tr->ref || (tr->current_trace && tr->current_trace->ref))
goto out_unlock;
list_del(&tr->list);

1
kernel/trace/trace.h
View File

@ -388,6 +388,7 @@ struct tracer {
struct tracer *next;
struct tracer_flags *flags;
int enabled;
int ref;
bool print_max;
bool allow_instances;
#ifdef CONFIG_TRACER_MAX_TRACE