linux-kernel - Re: [External] Re: [PATCH] riscv: Fix local irq restore when flags indicates irq disabled

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Date: Tue, 18 Jun 2024 13:05:49 +0200
From: Andrea Parri <parri.andrea@...il.com>
To: Alexandre Ghiti <alex@...ti.fr>
Cc: Xu Lu <luxu.kernel@...edance.com>, Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH] riscv: Fix local irq restore when flags
 indicates irq disabled

(merging replies)

> > > However, if local_irq_save() is called when irq is disabled. The SR_IE bit of
> > > flag returned is clear. If some code between local_irq_save() and
> > > local_irq_restore() reenables irq, causing the SR_IE bit of CSR_STATUS
> > > back to 1, then local_irq_restore() can not restore irq status back to disabled.

But doesn't that represent some bogus manipulation of the irq flags? cf.

config DEBUG_IRQFLAGS
	bool "Debug IRQ flag manipulation"
	help
	  Enables checks for potentially unsafe enabling or disabling of
	  interrupts, such as calling raw_local_irq_restore() when interrupts
	  are enabled.

in particular, raw_check_bogus_irq_restore() in raw_local_irq_restore().


> This got lost but this is still correct and needed.

You mean because of the mentioned rtl8723e example? are there other such
instances?  IOW, why do you say that the changes in question are needed?

  Andrea