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SubjectRe: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning
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On 3/1/16, Alan Stern <stern@rowland.harvard.edu> wrote:
> On Tue, 1 Mar 2016, Sedat Dilek wrote:
>
>> On Tue, Oct 13, 2015 at 2:57 AM, Steven Rostedt <rostedt@goodmis.org>
>> wrote:
>> > On Sat, 3 Oct 2015 12:05:42 +0200
>> > Sedat Dilek <sedat.dilek@gmail.com> wrote:
>> >
>> >> So, at the beginning... dunno WTF is causing the problems - no
>> >> workaround for CLANG.
>> >
>> > Probably need to compile with gcc and with clang and look at the binary
>> > differences. Or at least what objdump shows.
>> >
>>
>> [ Hope to address this issue to the correct people - CCed some people
>> I taped on their nerves ]
>>
>> Not sure if I should open a new thread?
>> Please, some clear statements on this.
>> Thanks.
>>
>> The issue is still visible and alive.
>
> ...
>
>> [ FACT #3: TEST-CASE #2 ]
>>
>> The most reliable test-case is to simply unplug my external Logitech
>> USB mouse - saw this by accident.
>> YES, it was so simple.
>>
>> --- dmesg_4.5.0-rc6-2-llvmlinux-amd64.txt 2016-02-29
>> 21:23:56.399691975 +0100
>> +++ dmesg_4.5.0-rc6-2-llvmlinux-amd64_usbmouse-unplugged.txt
>> 2016-02-29 21:28:14.401832240 +0100
>> @@ -832,3 +832,75 @@
>> [ 66.529779] PPP BSD Compression module registered
>> [ 66.563013] PPP Deflate Compression module registered
>> [ 66.978977] usb 2-1.5: USB disconnect, device number 4
>> +[ 321.937369] usb 2-1.4: USB disconnect, device number 3
>> +[ 321.950810] BUG: sleeping function called from invalid context at
>> kernel/workqueue.c:2785
>> +[ 321.950816] in_atomic(): 0, irqs_disabled(): 1, pid: 44, name:
>> kworker/2:1
>
>> +[ 321.950885] hardirqs last enabled at (47769):
>> [<ffffffff819426a2>] _raw_spin_unlock_irq+0x32/0x60
>> +[ 321.950889] hardirqs last disabled at (47770):
>> [<ffffffff81115bdc>] del_timer_sync+0x3c/0x110
>> +[ 321.950894] softirqs last enabled at (47112):
>> [<ffffffff810871a2>] __do_softirq+0x5a2/0x610
>> +[ 321.950898] softirqs last disabled at (47097):
>> [<ffffffff8108747c>] irq_exit+0x9c/0x120
>> +[ 321.950903] CPU: 2 PID: 44 Comm: kworker/2:1 Not tainted
>> 4.5.0-rc6-2-llvmlinux-amd64 #1
>> +[ 321.950905] Hardware name: SAMSUNG ELECTRONICS CO., LTD.
>> 530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013
>> +[ 321.950908] Workqueue: usb_hub_wq hub_event
>> +[ 321.950911] ffff8800d3326948 0000000000000092 0000000000000000
>> ffff8800d4347568
>> +[ 321.950915] ffffffff814ba7d4 ffff8800d43474f8 ffff8800d4340cc0
>> ffff8800d4347568
>> +[ 321.950919] ffffffff810e28fd 0000000000000092 0000000000000096
>> ffff8800d43475a8
>> +[ 321.950923] Call Trace:
>> +[ 321.950927] [<ffffffff814ba7d4>] dump_stack+0xa4/0xf0
>> +[ 321.950931] [<ffffffff810e28fd>] ? print_irqtrace_events+0xcd/0xe0
>> +[ 321.950936] [<ffffffff810bf495>] ___might_sleep+0x295/0x2b0
>> +[ 321.950939] [<ffffffff810bf18f>] __might_sleep+0x4f/0xc0
>> +[ 321.950943] [<ffffffff810a12ef>] start_flush_work+0x2f/0x2a0
>> +[ 321.950946] [<ffffffff810a129c>] flush_work+0x5c/0x80
>> +[ 321.950949] [<ffffffff810a125a>] ? flush_work+0x1a/0x80
>> +[ 321.950953] [<ffffffff810e247d>] ? trace_hardirqs_off+0xd/0x10
>> +[ 321.950956] [<ffffffff810a032a>] ? try_to_grab_pending+0x4a/0x260
>> +[ 321.950960] [<ffffffff810a1717>] __cancel_work_timer+0x197/0x290
>> +[ 321.950963] [<ffffffff81115b8d>] ? try_to_del_timer_sync+0xad/0xc0
>> +[ 321.950966] [<ffffffff810a1578>] cancel_work_sync+0x18/0x20
>
> It's possible that this could be a compiler-related error connected
> with local_irq_save(). __cancel_work_timer() calls
>
> ret = try_to_grab_pending(work, is_dwork, &flags);
>
> and try_to_grab_pending() starts this way:
>
> static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
> unsigned long *flags)
> {
> struct worker_pool *pool;
> struct pool_workqueue *pwq;
>
> local_irq_save(*flags);
>
> Then later on, __cancel_work_timer() does
>
> local_irq_restore(flags);
>
> Maybe CLANG doesn't like local_irq_save() applied to a pointer as
> opposed to a stack variable.
>
> As a quick test, try applying the patch below. (Note that there is a
> similar construction in kernel/signal.c.)
>
> Alan Stern
>
>
>
> Index: usb-4.4/kernel/workqueue.c
> ===================================================================
> --- usb-4.4.orig/kernel/workqueue.c
> +++ usb-4.4/kernel/workqueue.c
> @@ -1175,12 +1175,14 @@ out_put:
> * This function is safe to call from any context including IRQ handler.
> */
> static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
> - unsigned long *flags)
> + unsigned long *pflags)
> {
> struct worker_pool *pool;
> struct pool_workqueue *pwq;
> + unsigned long flags;
>
> - local_irq_save(*flags);
> + local_irq_save(flags);
> + *pflags = flags;
>
> /* try to steal the timer if it exists */
> if (is_dwork) {
> @@ -1241,7 +1243,7 @@ static int try_to_grab_pending(struct wo
> }
> spin_unlock(&pool->lock);
> fail:
> - local_irq_restore(*flags);
> + local_irq_restore(flags);
> if (work_is_canceling(work))
> return -ENOENT;
> cpu_relax();
>
>

might_sleep() is invoked in start_flush_work(), but there are no
"flags" passed to local_irq_{disable,enable}.

What about something like this?

@@ -2781,13 +2783,14 @@ static bool start_flush_work(struct
work_struct *work, struct wq_barrier *barr)
struct worker *worker = NULL;
struct worker_pool *pool;
struct pool_workqueue *pwq;
+ unsigned long flags;

might_sleep();

- local_irq_disable();
+ local_irq_disable(flags);
pool = get_work_pool(work);
if (!pool) {
- local_irq_enable();
+ local_irq_enable(flags);
return false;
}

- Sedat -
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