Re: [PATCH] sample-trace-array: Fix sleeping function called from invalid context
Hi Kefeng, Thanks for catching this issue. Please find my comments line - On 6/8/20 12:54 AM, Kefeng Wang wrote: > 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: 80001002bd90 (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 workqueueu to fix it. /s/workqueueu/workqueue Fixes: 89ed42495ef4 ("tracing: Sample module to demonstrate kernel access to Ftrace instances.") > Signed-off-by: Kefeng Wang > --- > samples/ftrace/sample-trace-array.c | 16 +++- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/samples/ftrace/sample-trace-array.c > b/samples/ftrace/sample-trace-array.c > index d523450d73eb..41684c7dbd7b 100644 > --- a/samples/ftrace/sample-trace-array.c > +++ b/samples/ftrace/sample-trace-array.c > @@ -20,6 +20,16 @@ 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 +39,7 @@ 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) I think we also need to use cancel_work_sync() to handle the case - 1. Module unloaded 2. Timer already ran and scheduled work to disable trace event 3. When the work runs we no longer have the relevant trace array. static int simple_thread(void *arg) { . del_timer(&mytimer); . return 0; } Thanks, Divya
Re: [PATCH] sample-trace-array: Fix sleeping function called from invalid context
Hi Steve, Sure, I am looking into it and reviewing the patch. Thanks, Divya On 6/8/20 7:37 AM, Steven Rostedt wrote: > On Mon, 8 Jun 2020 07:54:37 + > Kefeng Wang wrote: > >> 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: 80001002bd90 (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 workqueueu to fix it. >> >> Signed-off-by: Kefeng Wang >> > Divya, > > Can you give a Reviewed-by for this? > > -- Steve
Re: [PATCH] sample-trace-array: Fix sleeping function called from invalid context
On Mon, 8 Jun 2020 07:54:37 + Kefeng Wang wrote: > 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: 80001002bd90 (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 workqueueu to fix it. > > Signed-off-by: Kefeng Wang > Divya, Can you give a Reviewed-by for this? -- Steve
[PATCH] sample-trace-array: Fix sleeping function called from invalid context
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: 80001002bd90 (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 workqueueu to fix it. Signed-off-by: Kefeng Wang --- samples/ftrace/sample-trace-array.c | 16 +++- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/samples/ftrace/sample-trace-array.c b/samples/ftrace/sample-trace-array.c index d523450d73eb..41684c7dbd7b 100644 --- a/samples/ftrace/sample-trace-array.c +++ b/samples/ftrace/sample-trace-array.c @@ -20,6 +20,16 @@ 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 +39,7 @@ 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) -- 2.27.0