• Vincent Chen's avatar
    riscv: Avoid interrupts being erroneously enabled in handle_exception() · c82dd6d0
    Vincent Chen authored
    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: default avatarVincent Chen <vincent.chen@sifive.com>
    Reviewed-by: default avatarPalmer Dabbelt <palmer@sifive.com>
    [paul.walmsley@sifive.com: updated to apply]
    Fixes: bcae803a ("RISC-V: Enable IRQ during exception handling")
    Cc: David Abdurachmanov <david.abdurachmanov@sifive.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarPaul Walmsley <paul.walmsley@sifive.com>
    c82dd6d0
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