From: "Steven Rostedt (Red Hat)" <[email protected]> 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 <[email protected]> --- kernel/trace/trace.c | 16 +++++++++++++++- kernel/trace/trace.h | 1 + 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2e767972e99c..ed3fba1d6570 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -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); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 8de48bac1ce2..0eddfeb05fee 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -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 -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
