soc: qcom: smp2p: Safely acquire spinlock without IRQs

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.

Cc: stable@vger.kernel.org
Fixes: 50e99641413e7 ("soc: qcom: smp2p: Qualcomm Shared Memory Point to Point")
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Evan Green <evgreen@chromium.org>
Link: https://lore.kernel.org/r/20200929133040.RESEND.1.Ideabf6dcdfc577cf39ce3d95b0e4aa1ac8b38f0c@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

diff --git a/drivers/soc/qcom/smp2p.c b/drivers/soc/qcom/smp2p.c
index 07183d7..a9709aa 100644 (file)
--- 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);