[PATCH v2] mailbox: mtk-cmdq: Fix sleeping function called from invalid context

[Jason-JH Lin (林睿祥)]

Hi Krzysztof,

Thanks for the reviews.

On Wed, 2024-05-08 at 22:36 +0200, Krzysztof Kozlowski wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On 08/05/2024 11:51, Jason-JH.Lin wrote:
> > When we run kernel with lockdebug option, we will get the BUG
> below:
> > [  106.692124] BUG: sleeping function called from invalid context
> at drivers/base/power/runtime.c:1164
> > [  106.692190] in_atomic(): 1, irqs_disabled(): 128, non_block: 0,
> pid: 3616, name: kworker/u17:3
> 
> Trim logs from irrelevant context. timestamps are useless his.
> Registers
> as well. Addresses of stacktrace as well and better just decode it.
> 

OK, I'll remove the useless timestamps and registers.

> 
> > [  106.692226] preempt_count: 1, expected: 0
> > [  106.692254] RCU nest depth: 0, expected: 0
> > [  106.692282] INFO: lockdep is turned off.
> > [  106.692306] irq event stamp: 0
> > [  106.692331] hardirqs last  enabled at (0): [<0000000000000000>]
> 0x0
> > [  106.692376] hardirqs last disabled at (0): [<ffffffee15d37fa0>]
> copy_process+0xc90/0x2ac0
> > [  106.692429] softirqs last  enabled at (0): [<ffffffee15d37fc4>]
> copy_process+0xcb4/0x2ac0
> > [  106.692473] softirqs last disabled at (0): [<0000000000000000>]
> 0x0
> > [  106.692513] CPU: 1 PID: 3616 Comm: kworker/u17:3 Not tainted
> 6.1.87-lockdep-14133-g26e933aca785 #1
> 6839942e1cf34914b0a366137843dd2366f52aa9
> > [  106.692556] Hardware name: Google Ciri sku0/unprovisioned board
> (DT)
> > [  106.692586] Workqueue: imgsys_runner imgsys_runner_func
> > [  106.692638] Call trace:
> > [  106.692662]  dump_backtrace+0x100/0x120
> > [  106.692702]  show_stack+0x20/0x2c
> > [  106.692737]  dump_stack_lvl+0x84/0xb4
> > [  106.692775]  dump_stack+0x18/0x48
> > [  106.692809]  __might_resched+0x354/0x4c0
> > [  106.692847]  __might_sleep+0x98/0xe4
> > [  106.692883]  __pm_runtime_resume+0x70/0x124
> > [  106.692921]  cmdq_mbox_send_data+0xe4/0xb1c
> > [  106.692964]  msg_submit+0x194/0x2dc
> > [  106.693003]  mbox_send_message+0x190/0x330
> > [  106.693043]  imgsys_cmdq_sendtask+0x1618/0x2224
> > [  106.693082]  imgsys_runner_func+0xac/0x11c
> > [  106.693118]  process_one_work+0x638/0xf84
> > [  106.693158]  worker_thread+0x808/0xcd0
> > [  106.693196]  kthread+0x24c/0x324
> > [  106.693231]  ret_from_fork+0x10/0x20
> > 
> > We found that there is a spin_lock_irqsave protection in
> msg_submit()
> > of mailbox.c and it is in the atomic context.
> > So when cmdq driver calls pm_runtime_get_sync() in
> cmdq_mbox_send_data(),
> > it will get this BUG report.
> > 
> > 1. Change pm_runtime_get_sync() to pm_runtime_get() to avoid using
> sleep
> >    in atomic context.
> > 2. Move clk_bulk_enable() outside cmdq_runtime_resume() to ensure
> GCE
> >    clocks are enabled before configuring GCE register.
> > 3. Add used_count to avoid cmdq_runtime_suspend() being called
> before
> >    calling cmdq_runtime_resume().
> > 
> > Fixes: 8afe816b0c99 ("mailbox: mtk-cmdq-mailbox: Implement Runtime
> PM with autosuspend")
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin at mediatek.com>
> > ---
> >  drivers/mailbox/mtk-cmdq-mailbox.c | 24 +++++++++++++++---------
> >  1 file changed, 15 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/mailbox/mtk-cmdq-mailbox.c
> b/drivers/mailbox/mtk-cmdq-mailbox.c
> > index 033aff11f87c..b50f42e69aab 100644
> > --- a/drivers/mailbox/mtk-cmdq-mailbox.c
> > +++ b/drivers/mailbox/mtk-cmdq-mailbox.c
> > @@ -82,6 +82,7 @@ struct cmdq {
> >  const struct gce_plat*pdata;
> >  struct cmdq_thread*thread;
> >  struct clk_bulk_dataclocks[CMDQ_GCE_NUM_MAX];
> > +atomic_tused_count;
> >  boolsuspended;
> >  };
> >  
> > @@ -317,14 +318,21 @@ static int cmdq_runtime_resume(struct device
> *dev)
> >  {
> >  struct cmdq *cmdq = dev_get_drvdata(dev);
> >  
> > -return clk_bulk_enable(cmdq->pdata->gce_num, cmdq->clocks);
> > +atomic_inc(&cmdq->used_count);
> 
> Do not implement own runtime PM counter...
> 
> > +return 0;
> >  }
> >  
> >  static int cmdq_runtime_suspend(struct device *dev)
> >  {
> >  struct cmdq *cmdq = dev_get_drvdata(dev);
> >  
> > +if (atomic_read(&cmdq->used_count) == 0) {
> > +dev_warn(dev, "%s when used_count is 0!", __func__);
> > +return -EINVAL;
> > +}
> > +
> >  clk_bulk_disable(cmdq->pdata->gce_num, cmdq->clocks);
> > +atomic_dec(&cmdq->used_count);
> >  return 0;
> >  }
> >  
> > @@ -392,9 +400,8 @@ static int cmdq_mbox_send_data(struct mbox_chan
> *chan, void *data)
> >  /* Client should not flush new tasks if suspended. */
> >  WARN_ON(cmdq->suspended);
> >  
> > -ret = pm_runtime_get_sync(cmdq->mbox.dev);
> > -if (ret < 0)
> > -return ret;
> > +WARN_ON(pm_runtime_get(cmdq->mbox.dev) < 0);
> > +WARN_ON(clk_bulk_enable(cmdq->pdata->gce_num, cmdq->clocks));
> 
> That's a no... First, you remove error handling. Second, you add WARN
> and code should not have WARNs for error handling.

It should not use WARNs instead of error return. I'll revert this.

> 
> All this looks like terrible hacky workaround just to make warning go
> away, without actually addressing real problem.
> 

I think Angelo's idea is far better, so I'll try to implement the PM
function hook to achieve this.

Regards,
Jason-JH.Lin

> Best regards,
> Krzysztof
> 
>