ftrace: enable filtering only when a function is filtered on (e68746a2) · Commits · 戴 / test

Impact: fix to prevent empty set_ftrace_filter and no ftrace output The function filter is used to only trace a given set of functions. The filter is enabled when a function name is echoed into the set_ftrace_filter file. But if the name has a typo and the function is not found, the filter is enabled, but no function is listed. This makes a confusing situation where set_ftrace_filter is empty but no functions ever get enabled for tracing. For example: # cat /debug/tracing/set_ftrace_filter #### all functions enabled #### # echo bad_name > set_ftrace_filter # cat /debug/tracing/set_ftrace_filter # echo function > current_tracer # cat trace # tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | This patch changes that to only enable filtering if a function is set to be filtered on. Now, the filter is not enabled if a bad name is echoed into set_ftrace_filter. Signed-off-by:

Steven Rostedt <srostedt@redhat.com>

kernel/trace/ftrace.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -1153,8 +1153,6 @@ static void ftrace_match_records(char *buff, int len, int enable)

		/* should not be called from interrupt context */
		spin_lock(&ftrace_lock);
		if (enable)
		ftrace_filtered = 1;
		do_for_each_ftrace_rec(pg, rec) {

		if (rec->flags & FTRACE_FL_FAILED)
		@@ -1166,7 +1164,12 @@ static void ftrace_match_records(char *buff, int len, int enable)
		else
		rec->flags \|= flag;
		}

		/*
		* Only enable filtering if we have a function that
		* is filtered on.
		*/
		if (enable && (rec->flags & FTRACE_FL_FILTER))
		ftrace_filtered = 1;
		} while_for_each_ftrace_rec();
		spin_unlock(&ftrace_lock);
		}
		@@ -1217,9 +1220,6 @@ static void ftrace_match_module_records(char buff, char mod, int enable)

		/* should not be called from interrupt context */
		spin_lock(&ftrace_lock);
		if (enable)
		ftrace_filtered = 1;

		do_for_each_ftrace_rec(pg, rec) {

		if (rec->flags & FTRACE_FL_FAILED)
		@@ -1232,6 +1232,8 @@ static void ftrace_match_module_records(char buff, char mod, int enable)
		else
		rec->flags \|= flag;
		}
		if (enable && (rec->flags & FTRACE_FL_FILTER))
		ftrace_filtered = 1;

		} while_for_each_ftrace_rec();
		spin_unlock(&ftrace_lock);

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