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Message-ID: <CABb+yY1P5q8wHFOmTTR0sQnnS_gDeJB=f6tQ101bjY44qfHeDw@mail.gmail.com>
Date: Tue, 30 Apr 2024 19:57:54 -0500
From: Jassi Brar <jassisinghbrar@...il.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: "Jason-JH.Lin" <jason-jh.lin@...iatek.com>, Chun-Kuang Hu <chunkuang.hu@...nel.org>,
Matthias Brugger <matthias.bgg@...il.com>, Jason-ch Chen <jason-ch.chen@...iatek.com>,
Singo Chang <singo.chang@...iatek.com>, Nancy Lin <nancy.lin@...iatek.com>,
Shawn Sung <shawn.sung@...iatek.com>, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH] mailbox: mtk-cmdq: Fix sleeping function called from
invalid context
On Tue, Apr 30, 2024 at 4:39 AM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> Il 30/04/24 10:39, Jason-JH.Lin ha scritto:
> > 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
> > [ 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.
> > So when cmdq driver calls pm_runtime_get_sync() in cmdq_mbox_send_data(),
> > it will get this BUG report.
> >
> > Add pm_runtime_irq_safe() to let pm_runtime callbacks is safe in atomic
> > context with interrupts disabled.
> >
>
> I see. The problem with this is that pm_runtime_irq_safe() will raise the refcount
> of the parent device "forever", which isn't the best and partially defeats what we
> are trying to do here (keeping stuff off unless really needed).
>
> At this point I wonder if it'd be just better to really fix this instead of working
> around the problem.
>
> I'd say that one of the options would be to perform a change to msg_submit() so
> that it will take into account that a .send_data() callback might be using RPM
> functions.
>
> Ideas? :-)
>
@send_data: The API asks the MBOX controller driver, in atomic
* context try to transmit a message on the bus. Returns 0 if
* data is accepted for transmission, -EBUSY while rejecting
* if the remote hasn't yet read the last data sent. Actual
* transmission of data is reported by the controller via
* mbox_chan_txdone (if it has some TX ACK irq). It must not
* sleep.
As long as send_data() does not sleep, ideas are welcome.
Cheers.
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