Re: [PATCH] scsi: ufs: core: Avoid sleeping in hard interrupt context when PREEMP_RT is enabled.

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2026-07-06 07:30:48 [-0700], Bart Van Assche wrote:
> On 6/30/26 7:15 AM, Sebastian Andrzej Siewior wrote:
> >  From ufshcd_intr():
> > |         intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
> > |         enabled_intr_status = intr_status & ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
> > |
> > |         ufshcd_writel(hba, intr_status, REG_INTERRUPT_STATUS);
> > 
> > What does this do? Does it disable the IRQ source? If so then
> > IRQF_ONESHOT should be removed.
> 
> Writing into the REG_INTERRUPT_STATUS register clears the bits that are
> set in the first argument of writel().

This makes it sounds as it would acknowledge the interrupt. If that is
the case then there is no need for IRQF_ONESHOT.

> > |         /* Directly handle interrupts since MCQ ESI handlers does the hard job */
> > |         return ufshcd_sl_intr(hba, enabled_intr_status);
> > 
> > If not, why is this not part of the threaded handler?
> If MCQ is disabled, ufshcd_sl_intr() processes all types of interrupts.
> If MCQ is enabled, the ESI interrupt handlers process I/O completions
> and ufshcd_sl_intr() processes the remaining interrupt types.

So MCQ is the trigger. Does its status change after device's init time?

If I understood it correctly, after the REG_INTERRUPT_STATUS there is no
need for IRQF_ONESHOT since this masks the interrupt until the thread is
done.

If MCQ disabled there is no need for this ACK and the it could be just a
request_irq(, ufshcd_sl_intr).

If MCQ is enabled then request_threaded_irq(, mask_interrupt_only,
   ufshcd_threaded_intr, IRQF_NO_THREAD)

Would this work?

> Bart.

Sebastian