[PATCH 4.19 322/346] soc: qcom: smp2p: Safely acquire spinlock without IRQs

Greg Kroah-Hartman
2020-12-28T13:37:33Z

From: Evan Green <evgreen@chromium.org>

commit fc3e62e25c3896855b7c3d72df19ca6be3459c9f upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/soc/qcom/smp2p.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/soc/qcom/smp2p.c
+++ b/drivers/soc/qcom/smp2p.c
@@ -326,15 +326,16 @@ static int qcom_smp2p_inbound_entry(stru
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);