Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4c27e756 authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
Browse files

tracing: Move locking of trace_cmdline_lock into start/stop seq calls 



With the conversion of the saved_cmdlines output to use seq_read, there
is now a race between accessing the values of the saved_cmdlines and
the writing to them. The trace_cmdline_lock needs to be taken at
the start and stop of the seq calls.

A new __trace_find_cmdline() call is created to allow for the look up
to happen without taking the lock.

Fixes: 42584c81 tracing: Have saved_cmdlines use the seq_read infrastructure
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 379cfdac

kernel/trace/trace.c

+15 −4
Original line number Diff line number Diff line
@@ -1484,7 +1484,7 @@ static int trace_save_cmdline(struct task_struct *tsk) 
	return 1;

}



void trace_find_cmdline(int pid, char comm[])

static void __trace_find_cmdline(int pid, char comm[])

{

	unsigned map;
@@ -1503,13 +1503,19 @@ void trace_find_cmdline(int pid, char comm[]) 
		return;

	}



	preempt_disable();

	arch_spin_lock(&trace_cmdline_lock);

	map = map_pid_to_cmdline[pid];

	if (map != NO_CMDLINE_MAP)

		strcpy(comm, saved_cmdlines[map]);

	else

		strcpy(comm, "<...>");

}



void trace_find_cmdline(int pid, char comm[])

{

	preempt_disable();

	arch_spin_lock(&trace_cmdline_lock);



	__trace_find_cmdline(pid, comm);



	arch_spin_unlock(&trace_cmdline_lock);

	preempt_enable();
@@ -3724,6 +3730,9 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos) 
	void *v;

	loff_t l = 0;



	preempt_disable();

	arch_spin_lock(&trace_cmdline_lock);



	v = &map_cmdline_to_pid[0];

	while (l <= *pos) {

		v = saved_cmdlines_next(m, v, &l);
@@ -3736,6 +3745,8 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos) 


static void saved_cmdlines_stop(struct seq_file *m, void *v)

{

	arch_spin_unlock(&trace_cmdline_lock);

	preempt_enable();

}



static int saved_cmdlines_show(struct seq_file *m, void *v)
@@ -3743,7 +3754,7 @@ static int saved_cmdlines_show(struct seq_file *m, void *v) 
	char buf[TASK_COMM_LEN];

	unsigned int *pid = v;



	trace_find_cmdline(*pid, buf);

	__trace_find_cmdline(*pid, buf);

	seq_printf(m, "%d %s\n", *pid, buf);

	return 0;

}