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Message-ID: <20230816180944.19262-1-fancer.lancer@gmail.com>
Date: Wed, 16 Aug 2023 21:09:40 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Andrew Lunn <andrew@...n.ch>,
Heiner Kallweit <hkallweit1@...il.com>,
Russell King <linux@...linux.org.uk>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Francesco Dolcini <francesco.dolcini@...adex.com>
Cc: Serge Semin <fancer.lancer@...il.com>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [RFC net] Revert "net: phy: Fix race condition on link status change"
Protecting the phy_driver.drv->handle_interrupt() callback invocation by
the phy_device.lock mutex causes all the IRQ-capable PHY drivers to lock
the mutex twice thus deadlocking on the next calls thread:
IRQ: phy_interrupt()
+-> mutex_lock(&phydev->lock); <-------------+
drv->handle_interrupt() | Deadlock due to the
+-> phy_error() + nested PHY-device
+-> phy_process_error() | mutex lock
+-> mutex_lock(&phydev->lock); <-+
phydev->state = PHY_ERROR;
mutex_unlock(&phydev->lock);
mutex_unlock(&phydev->lock);
The problem can be easily reproduced just by calling phy_error() from the
any PHY-device interrupt handler. Reverting the commit 91a7cda1f4b8 ("net:
phy: Fix race condition on link status change") fixes the deadlock.
This reverts commit 91a7cda1f4b8bdf770000a3b60640576dafe0cec.
Fixes: 91a7cda1f4b8 ("net: phy: Fix race condition on link status change")
Signed-off-by: Serge Semin <fancer.lancer@...il.com>
---
Since obviously it would be better to fix both the deadlock and the
problem described in the blamed commit the patch is marked as RFC. I am
not aware of a better solution for now than to revert the commit caused
the regression. So let's discuss to find out whether it's possible to have
a better fix here.
---
drivers/net/phy/phy.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index bdf00b2b2c1d..9483bd57158e 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -1235,7 +1235,6 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
{
struct phy_device *phydev = phy_dat;
struct phy_driver *drv = phydev->drv;
- irqreturn_t ret;
/* Wakeup interrupts may occur during a system sleep transition.
* Postpone handling until the PHY has resumed.
@@ -1259,11 +1258,7 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
return IRQ_HANDLED;
}
- mutex_lock(&phydev->lock);
- ret = drv->handle_interrupt(phydev);
- mutex_unlock(&phydev->lock);
-
- return ret;
+ return drv->handle_interrupt(phydev);
}
/**
--
2.41.0
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