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From:   Song Shuai <songshuaishuai@tinylab.org>
To:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, guoren@kernel.org,
        xianting.tian@linux.alibaba.com, takahiro.akashi@linaro.org
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        Song Shuai <songshuaishuai@tinylab.org>
Subject: [PATCH -fixes] riscv: kexec: Avoid deadlock in kexec crash path
Date:   Fri,  8 Dec 2023 19:10:15 +0800
Message-Id: <20231208111015.173237-1-songshuaishuai@tinylab.org>
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If the kexec crash code is called in the interrupt context, the
machine_kexec_mask_interrupts() function will trigger a deadlock while
trying to acquire the irqdesc spinlock and then deacitive irqchip.

To avoid the deadlock, this patch directly EOI the irq regardless of
the active status of irqchip.

Fixes: b17d19a5314a ("riscv: kexec: Fixup irq controller broken in kexec crash path")
Signed-off-by: Song Shuai <songshuaishuai@tinylab.org>
---
Note that:
   
1. this deadlock can reproduced via echo EXCEPTION to lkdtm INT_HW_IRQ_EN point
   
2. RISC-V HLIC and PLIC irqchips don't have the irq_set_irqchip_state handler
and I don't know is it ok to deactive irqchip without the spinlock in this
code context, so I simply removed that snippet as arm and powerpc do.

I would like to listen to your advice.
---
 arch/riscv/kernel/machine_kexec.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
index f6c7135b00d7..d7ddf4d2b243 100644
--- a/arch/riscv/kernel/machine_kexec.c
+++ b/arch/riscv/kernel/machine_kexec.c
@@ -149,20 +149,12 @@ static void machine_kexec_mask_interrupts(void)
 
 	for_each_irq_desc(i, desc) {
 		struct irq_chip *chip;
-		int ret;
 
 		chip = irq_desc_get_chip(desc);
 		if (!chip)
 			continue;
 
-		/*
-		 * First try to remove the active state. If this
-		 * fails, try to EOI the interrupt.
-		 */
-		ret = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
-
-		if (ret && irqd_irq_inprogress(&desc->irq_data) &&
-		    chip->irq_eoi)
+		if (chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
 			chip->irq_eoi(&desc->irq_data);
 
 		if (chip->irq_mask)
-- 
2.20.1