On 3/2/16, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> On 3/1/16, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>> On Tue, 1 Mar 2016, Sedat Dilek wrote:
>>
>>> On Tue, Oct 13, 2015 at 2:57 AM, Steven Rostedt <rostedt@xxxxxxxxxxx>
>>> wrote:
>>> > On Sat, 3 Oct 2015 12:05:42 +0200
>>> > Sedat Dilek <sedat.dilek@xxxxxxxxx> 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;
> }
>
start_flush_work() is the only place where no flags are passed.
That stuff above does not work - no clue how to do that.
Any help?
Then I see there...
...
spin_lock(&pool->lock);
...
spin_unlock_irq(&pool->lock);
...
Should that be spin_lock_irq()?
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;
might_sleep();
local_irq_disable();
pool = get_work_pool(work);
if (!pool) {
local_irq_enable();
return false;
}
spin_lock(&pool->lock); <--- XXX: spin_lock_irq() ???
/* see the comment in try_to_grab_pending() with the same code */
pwq = get_work_pwq(work);
if (pwq) {
if (unlikely(pwq->pool != pool))
goto already_gone;
} else {
worker = find_worker_executing_work(pool, work);
if (!worker)
goto already_gone;
pwq = worker->current_pwq;
}
check_flush_dependency(pwq->wq, work);
insert_wq_barrier(pwq, barr, work, worker);
spin_unlock_irq(&pool->lock);
/*
* If @max_active is 1 or rescuer is in use, flushing another work
* item on the same workqueue may lead to deadlock. Make sure the
* flusher is not running on the same workqueue by verifying write
* access.
*/
if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
lock_map_acquire(&pwq->wq->lockdep_map);
else
lock_map_acquire_read(&pwq->wq->lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);
return true;
already_gone:
spin_unlock_irq(&pool->lock);
return false;
}
- Sedat -
--
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