On Tue 29 Sep 15:30 CDT 2020, Evan Green wrote:
> smp2p_update_bits() should disable interrupts when it acquires its
> spinlock. This is important because without the _irqsave, a priority
> inversion can occur.
>
> This function is called both with interrupts enabled in
> qcom_q6v5_request_stop(), and with interrupts disabled in
> ipa_smp2p_panic_notifier(). IRQ handling of spinlocks should be
> consistent to avoid the panic notifier deadlocking because it's
> sitting on the thread that's already got the lock via _request_stop().
>
> Found via lockdep.
>
> Fixes: 50e99641413e7 ("soc: qcom: smp2p: Qualcomm Shared Memory Point to Point")
> Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx>
Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Regards,
Bjorn
> ---
>
> drivers/soc/qcom/smp2p.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/soc/qcom/smp2p.c b/drivers/soc/qcom/smp2p.c
> index 07183d731d747..a9709aae54abb 100644
> --- a/drivers/soc/qcom/smp2p.c
> +++ b/drivers/soc/qcom/smp2p.c
> @@ -318,15 +318,16 @@ static int qcom_smp2p_inbound_entry(struct qcom_smp2p *smp2p,
> static int smp2p_update_bits(void *data, u32 mask, u32 value)
> {
> struct smp2p_entry *entry = data;
> + unsigned long flags;
> u32 orig;
> u32 val;
>
> - spin_lock(&entry->lock);
> + spin_lock_irqsave(&entry->lock, flags);
> val = orig = readl(entry->value);
> val &= ~mask;
> val |= value;
> writel(val, entry->value);
> - spin_unlock(&entry->lock);
> + spin_unlock_irqrestore(&entry->lock, flags);
>
> if (val != orig)
> qcom_smp2p_kick(entry->smp2p);
> --
> 2.26.2
>
