diff options
| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2021-01-29 10:13:53 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-02-23 14:00:29 +0100 |
| commit | 7ffd979613681d33dc9f71becd817cfd54734103 (patch) | |
| tree | 22c20c1e1db9fc1f4663ddfff2c822bbd7d7eb54 /include | |
| parent | 29c52025152bab4c557d8174da58f1a4c8e70438 (diff) | |
fgraph: Initialize tracing_graph_pause at task creation
commit 7e0a9220467dbcfdc5bc62825724f3e52e50ab31 upstream.
On some archs, the idle task can call into cpu_suspend(). The cpu_suspend()
will disable or pause function graph tracing, as there's some paths in
bringing down the CPU that can have issues with its return address being
modified. The task_struct structure has a "tracing_graph_pause" atomic
counter, that when set to something other than zero, the function graph
tracer will not modify the return address.
The problem is that the tracing_graph_pause counter is initialized when the
function graph tracer is enabled. This can corrupt the counter for the idle
task if it is suspended in these architectures.
CPU 1 CPU 2
----- -----
do_idle()
cpu_suspend()
pause_graph_tracing()
task_struct->tracing_graph_pause++ (0 -> 1)
start_graph_tracing()
for_each_online_cpu(cpu) {
ftrace_graph_init_idle_task(cpu)
task-struct->tracing_graph_pause = 0 (1 -> 0)
unpause_graph_tracing()
task_struct->tracing_graph_pause-- (0 -> -1)
The above should have gone from 1 to zero, and enabled function graph
tracing again. But instead, it is set to -1, which keeps it disabled.
There's no reason that the field tracing_graph_pause on the task_struct can
not be initialized at boot up.
Cc: stable@vger.kernel.org
Fixes: 380c4b1411ccd ("tracing/function-graph-tracer: append the tracing_graph_flag")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211339
Reported-by: pierre.gondois@arm.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/ftrace.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index e54d257983f2..2c9f2ddd62f9 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -792,7 +792,9 @@ typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER /* for init task */ -#define INIT_FTRACE_GRAPH .ret_stack = NULL, +#define INIT_FTRACE_GRAPH \ + .ret_stack = NULL, \ + .tracing_graph_pause = ATOMIC_INIT(0), /* * Stack of return addresses for functions |