From: Evan Green <evgreen@chromium.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Markus Elfring <elfring@users.sourceforge.net>,
Evan Green <evgreen@chromium.org>, Andy Gross <agross@kernel.org>,
linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] soc: qcom: smp2p: Safely acquire spinlock without IRQs
Date: Mon, 8 Jun 2020 14:57:36 -0700 [thread overview]
Message-ID: <20200608145653.1.Ideabf6dcdfc577cf39ce3d95b0e4aa1ac8b38f0c@changeid> (raw)
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@chromium.org>
---
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);
--
2.24.1
reply other threads:[~2020-06-08 21:57 UTC|newest]
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