From: Kefeng Wang wangkefeng.wang@huawei.com
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:935 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 0, name: swapper/5 1 lock held by swapper/5/0: #0: ffff80001002bd90 (samples/ftrace/sample-trace-array.c:38){+.-.}-{0:0}, at: call_timer_fn+0x8/0x3e0 CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.7.0+ #8 Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: dump_backtrace+0x0/0x1a0 show_stack+0x20/0x30 dump_stack+0xe4/0x150 ___might_sleep+0x160/0x200 __might_sleep+0x58/0x90 __mutex_lock+0x64/0x948 mutex_lock_nested+0x3c/0x58 __ftrace_set_clr_event+0x44/0x88 trace_array_set_clr_event+0x24/0x38 mytimer_handler+0x34/0x40 [sample_trace_array]
mutex_lock() will be called in interrupt context, using workqueue to fix it.
Link: https://lkml.kernel.org/r/20200610011244.2209486-1-wangkefeng.wang@huawei.co...
Cc: stable@vger.kernel.org Fixes: 89ed42495ef4 ("tracing: Sample module to demonstrate kernel access to Ftrace instances.") Reviewed-by: Divya Indi divya.indi@oracle.com Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- samples/ftrace/sample-trace-array.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/samples/ftrace/sample-trace-array.c b/samples/ftrace/sample-trace-array.c index d523450d73eb..9e437f930280 100644 --- a/samples/ftrace/sample-trace-array.c +++ b/samples/ftrace/sample-trace-array.c @@ -6,6 +6,7 @@ #include <linux/timer.h> #include <linux/err.h> #include <linux/jiffies.h> +#include <linux/workqueue.h>
/* * Any file that uses trace points, must include the header. @@ -20,6 +21,16 @@ struct trace_array *tr; static void mytimer_handler(struct timer_list *unused); static struct task_struct *simple_tsk;
+static void trace_work_fn(struct work_struct *work) +{ + /* + * Disable tracing for event "sample_event". + */ + trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", + false); +} +static DECLARE_WORK(trace_work, trace_work_fn); + /* * mytimer: Timer setup to disable tracing for event "sample_event". This * timer is only for the purposes of the sample module to demonstrate access of @@ -29,11 +40,7 @@ static DEFINE_TIMER(mytimer, mytimer_handler);
static void mytimer_handler(struct timer_list *unused) { - /* - * Disable tracing for event "sample_event". - */ - trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", - false); + schedule_work(&trace_work); }
static void simple_thread_func(int count) @@ -76,6 +83,7 @@ static int simple_thread(void *arg) simple_thread_func(count++);
del_timer(&mytimer); + cancel_work_sync(&trace_work);
/* * trace_array_put() decrements the reference counter associated with