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([2a0d:3344:244b:910::f39]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a099ae0ca4sm20112152f8f.14.2025.05.08.03.41.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 May 2025 03:41:46 -0700 (PDT) Message-ID: <14c78296-97a0-46b4-b2aa-0ac8fa026d59@redhat.com> Date: Thu, 8 May 2025 12:41:45 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: cadence: macb: Fix a possible deadlock in macb_halt_tx. To: Mathieu Othacehe , Nicolas Ferre Cc: Claudiu Beznea , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, anton.reding@landisgyr.com References: <20250507101231.12578-1-othacehe@gnu.org> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250507101231.12578-1-othacehe@gnu.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/7/25 12:12 PM, Mathieu Othacehe wrote: > There is a situation where after THALT is set high, TGO stays high as > well. Because jiffies are never updated, as we are in a context with > interrupts disabled, we never exit that loop and have a deadlock. > > That deadlock was noticed on a sama5d4 device that stayed locked for days. > > Use retries instead of jiffies so that the timeout really works and we do > not have a deadlock anymore. > > Signed-off-by: Mathieu Othacehe This looks like a fix that should target the net tree and include a fixes tag, see Documentation/process/maintainer-netdev.rst > --- > drivers/net/ethernet/cadence/macb_main.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c > index 1fe8ec37491b1..ffcf569c14f6a 100644 > --- a/drivers/net/ethernet/cadence/macb_main.c > +++ b/drivers/net/ethernet/cadence/macb_main.c > @@ -997,20 +997,19 @@ static void macb_update_stats(struct macb *bp) > > static int macb_halt_tx(struct macb *bp) > { > - unsigned long halt_time, timeout; > - u32 status; > + unsigned int delay_us = 250; > + unsigned int retries = MACB_HALT_TIMEOUT / delay_us; > + u32 status; > > macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(THALT)); > > - timeout = jiffies + usecs_to_jiffies(MACB_HALT_TIMEOUT); > do { > - halt_time = jiffies; > status = macb_readl(bp, TSR); > if (!(status & MACB_BIT(TGO))) > return 0; > > - udelay(250); > - } while (time_before(halt_time, timeout)); > + udelay(delay_us); > + } while (retries-- > 0); I think it would be better to use read_poll_timeout_atomic() instead of sort-of open-codying it. Thanks, Paolo