From: Vincent Chen vincent.chen@sifive.com
[ Upstream commit c82dd6d078a2bb29d41eda032bb96d05699a524d ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/kernel/entry.S | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index bc7a56e1ca6f4..9b60878a4469c 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 sstatus, SR_SIE
+1: /* Handle syscalls */ li t0, EXC_SYSCALL beq s4, t0, handle_syscall