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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id i5sm1252465ooo.32.2020.10.16.10.18.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Oct 2020 10:18:47 -0700 (PDT) Date: Fri, 16 Oct 2020 12:13:37 -0500 From: Bjorn Andersson To: Evan Green Cc: Markus Elfring , Andy Gross , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH] soc: qcom: smp2p: Safely acquire spinlock without IRQs Message-ID: <20201016171337.GA241575@builder.lan> References: <20200929133040.RESEND.1.Ideabf6dcdfc577cf39ce3d95b0e4aa1ac8b38f0c@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200929133040.RESEND.1.Ideabf6dcdfc577cf39ce3d95b0e4aa1ac8b38f0c@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org 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 Reviewed-by: Bjorn Andersson 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 >