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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2021-01-29 10:13:53 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-02-10 09:25:29 +0100 |
| commit | e80f9021d5be80b05c8f75709d23811a831af565 (patch) | |
| tree | 604b02d4084f3141dff2a78d5852e2d567ce16bc | |
| parent | efa17285b3384607cfa4e5eabccb4f84b1489009 (diff) | |
| download | linux-stable-e80f9021d5be80b05c8f75709d23811a831af565.tar.gz linux-stable-e80f9021d5be80b05c8f75709d23811a831af565.tar.bz2 linux-stable-e80f9021d5be80b05c8f75709d23811a831af565.zip | |
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>
| -rw-r--r-- | init/init_task.c | 3 | ||||
| -rw-r--r-- | kernel/trace/fgraph.c | 2 |
2 files changed, 2 insertions, 3 deletions
diff --git a/init/init_task.c b/init/init_task.c index df7041be96fc..5d8359c44564 100644 --- a/init/init_task.c +++ b/init/init_task.c @@ -171,7 +171,8 @@ struct task_struct init_task .lockdep_recursion = 0, #endif #ifdef CONFIG_FUNCTION_GRAPH_TRACER - .ret_stack = NULL, + .ret_stack = NULL, + .tracing_graph_pause = ATOMIC_INIT(0), #endif #if defined(CONFIG_TRACING) && defined(CONFIG_PREEMPTION) .trace_recursion = 0, diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 7950a0356042..888cd00174fe 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -367,7 +367,6 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) } if (t->ret_stack == NULL) { - atomic_set(&t->tracing_graph_pause, 0); atomic_set(&t->trace_overrun, 0); t->curr_ret_stack = -1; t->curr_ret_depth = -1; @@ -462,7 +461,6 @@ static DEFINE_PER_CPU(struct ftrace_ret_stack *, idle_ret_stack); static void graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack) { - atomic_set(&t->tracing_graph_pause, 0); atomic_set(&t->trace_overrun, 0); t->ftrace_timestamp = 0; /* make curr_ret_stack visible before we add the ret_stack */ |