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    Subject[PATCH 5.7 468/477] sample-trace-array: Fix sleeping function called from invalid context
    Date
    From: Kefeng Wang <wangkefeng.wang@huawei.com>

    commit e9b7b1c0c103a623be1a65c39f98719803440871 upstream.

    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.com

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    samples/ftrace/sample-trace-array.c | 18 +++++++++++++-----
    1 file changed, 13 insertions(+), 5 deletions(-)

    --- 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_han

    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

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