Re: [External] Re: [PATCH] riscv: Fix local irq restore when flags indicates irq disabled
From: Alexandre Ghiti
Date: Tue Jun 18 2024 - 07:16:15 EST
On 18/06/2024 12:00, Xu Lu wrote:
Hi Alex,
I will send a new version later today.
Great, thanks, I'll make sure it lands in -fixes.
Sorry it did not get merged sooner.
Thanks,
Alex
Thanks,
Xu Lu
On Tue, Jun 18, 2024 at 5:45 PM Alexandre Ghiti <alex@xxxxxxxx> wrote:
Hi Xu Lu,
On 24/08/2023 14:08, Xu Lu wrote:
On Wed, Aug 9, 2023 at 2:58 PM 旭路 <luxu.kernel@xxxxxxxxxxxxx> wrote:
On Wed, Aug 9, 2023 at 2:05 PM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
On Tue, 25 Jul 2023 00:05:49 PDT (-0700), luxu.kernel@xxxxxxxxxxxxx wrote:
When arch_local_irq_restore() is called with flags indicating irqs
disabled, we need to clear SR_IE bit in CSR_STATUS, whereas current
implementation based on csr_set() function only sets SR_IE bit of
CSR_STATUS when SR_IE bit of flags is high and does nothing when
SR_IE bit of flags is low.
This commit supplies csr clear operation when calling irq restore
function with flags indicating irq disabled.
Fixes: 6d60b6ee0c97 ("RISC-V: Device, timer, IRQs, and the SBI")
Signed-off-by: Xu Lu <luxu.kernel@xxxxxxxxxxxxx>
---
arch/riscv/include/asm/irqflags.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/irqflags.h b/arch/riscv/include/asm/irqflags.h
index 08d4d6a5b7e9..7c31fc3c3559 100644
--- a/arch/riscv/include/asm/irqflags.h
+++ b/arch/riscv/include/asm/irqflags.h
@@ -49,7 +49,10 @@ static inline int arch_irqs_disabled(void)
/* set interrupt enabled status */
static inline void arch_local_irq_restore(unsigned long flags)
{
- csr_set(CSR_STATUS, flags & SR_IE);
+ if (flags & SR_IE)
+ csr_set(CSR_STATUS, SR_IE);
+ else
+ csr_clear(CSR_STATUS, SR_IE);
Unless I'm missing something, the original version is correct:
local_irq_restore() must be paired with a local_irq_save(), so we can
only get here with interrupts disabled.
Yes, it is correct if local_irq_save() is called when irq is enabled before.
The flags returned will be SR_IE. And it is safe to call local_irq_restore()
with flag SR_IE in any case.
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.
Here is an example in existing driver (may not belong to riscv arch) in
drivers/net/wireless/realtek/rtlwifi/rtl8723ae/hw.c. The pseudo code
behaves like:
int rtl8723e_hw_init(struct ieee80211_hw *hw)
{
int err;
unsigned long flags;
...
local_irq_save_flags(flags);
local_irq_enable();
...
local_irq_restore(flags);
...
return err;
}
}
#endif /* _ASM_RISCV_IRQFLAGS_H */
A gentle ping.
This got lost but this is still correct and needed.
Do you think you can respin a new version? Otherwise, I'll do it and
keep you SoB.
Thanks,
Alex
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