On Tue, Oct 08, 2019 at 07:27:44PM +0200, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 5.3-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c82dd6d078a2bb29d41eda032bb96d05699a524d Mon Sep 17 00:00:00 2001 From: Vincent Chen vincent.chen@sifive.com Date: Mon, 16 Sep 2019 16:47:41 +0800 Subject: [PATCH] riscv: Avoid interrupts being erroneously enabled in handle_exception()

When the handle_exception function addresses an exception, the interrupts will be unconditionally enabled after finishing the context save. However, It may erroneously enable the interrupts if the interrupts are disabled before entering the handle_exception.

For example, one of the WARN_ON() condition is satisfied in the scheduling where the interrupt is disabled and rq.lock is locked. The WARN_ON will trigger a break exception and the handle_exception function will enable the interrupts before entering do_trap_break function. During the procedure, if a timer interrupt is pending, it will be taken when interrupts are enabled. In this case, it may cause a deadlock problem if the rq.lock is locked again in the timer ISR.

Hence, the handle_exception() can only enable interrupts when the state of sstatus.SPIE is 1.

This patch is tested on HiFive Unleashed board.

Signed-off-by: Vincent Chen vincent.chen@sifive.com Reviewed-by: Palmer Dabbelt palmer@sifive.com [paul.walmsley@sifive.com: updated to apply] Fixes: bcae803a21317 ("RISC-V: Enable IRQ during exception handling") Cc: David Abdurachmanov david.abdurachmanov@sifive.com Cc: stable@vger.kernel.org Signed-off-by: Paul Walmsley paul.walmsley@sifive.com

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 74ccfd464071..da7aa88113c2 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -166,9 +166,13 @@ ENTRY(handle_exception) move a0, sp /* pt_regs */ tail do_IRQ 1:

• /* Exceptions run with interrupts enabled */

• /* Exceptions run with interrupts enabled or disabled

•   depending on the state of sstatus.SR_SPIE */
  

• andi t0, s1, SR_SPIE
• beqz t0, 1f csrs CSR_SSTATUS, SR_SIE

+1:

I might be missing something here, but wasn't the label "1" already declared a few lines above?

-- Thanks, Sasha