From 0ac49527318bc388a881152d60f49d7951606024 Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Fri, 28 Sep 2007 22:42:14 -0700 Subject: [PATCH] PHYLIB: IRQ event workqueue handling fixes Keep track of disable_irq_nosync() invocations and call enable_irq() the right number of times if work has been cancelled that would include them. Now that the call to flush_work_keventd() (problematic because of rtnl_mutex being held) has been replaced by cancel_work_sync() another issue has arisen and been left unresolved. As the MDIO bus cannot be accessed from the interrupt context the PHY interrupt handler uses disable_irq_nosync() to prevent from looping and schedules some work to be done as a softirq, which, apart from handling the state change of the originating PHY, is responsible for reenabling the interrupt. Now if the interrupt line is shared by another device and a call to the softirq handler has been cancelled, that call to enable_irq() never happens and the other device cannot use its interrupt anymore as its stuck disabled. I decided to use a counter rather than a flag because there may be more than one call to phy_change() cancelled in the queue -- a real one and a fake one triggered by free_irq() if DEBUG_SHIRQ is used, if nothing else. Therefore because of its nesting property enable_irq() has to be called the right number of times to match the number disable_irq_nosync() was called and restore the original state. This DEBUG_SHIRQ feature is also the reason why free_irq() has to be called before cancel_work_sync(). While at it I updated the comment about phy_stop_interrupts() being called from `keventd' -- this is no longer relevant as the use of cancel_work_sync() makes such an approach unnecessary. OTOH a similar comment referring to flush_scheduled_work() in phy_stop() still applies as using cancel_work_sync() there would be dangerous. Checked with checkpatch.pl and at the run time (with and without DEBUG_SHIRQ). Signed-off-by: Maciej W. Rozycki Cc: Andy Fleming Cc: Jeff Garzik Signed-off-by: Andrew Morton Signed-off-by: Jeff Garzik --- drivers/net/phy/phy.c | 24 +++++++++++++++++++----- include/linux/phy.h | 3 +++ 2 files changed, 22 insertions(+), 5 deletions(-) diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c index 4da993dfcfd8..5a314edc2744 100644 --- a/drivers/net/phy/phy.c +++ b/drivers/net/phy/phy.c @@ -7,7 +7,7 @@ * Author: Andy Fleming * * Copyright (c) 2004 Freescale Semiconductor, Inc. - * Copyright (c) 2006 Maciej W. Rozycki + * Copyright (c) 2006, 2007 Maciej W. Rozycki * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the @@ -35,6 +35,7 @@ #include #include +#include #include #include #include @@ -562,6 +563,7 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat) * queue will write the PHY to disable and clear the * interrupt, and then reenable the irq line. */ disable_irq_nosync(irq); + atomic_inc(&phydev->irq_disable); schedule_work(&phydev->phy_queue); @@ -632,6 +634,7 @@ int phy_start_interrupts(struct phy_device *phydev) INIT_WORK(&phydev->phy_queue, phy_change); + atomic_set(&phydev->irq_disable, 0); if (request_irq(phydev->irq, phy_interrupt, IRQF_SHARED, "phy_interrupt", @@ -662,13 +665,22 @@ int phy_stop_interrupts(struct phy_device *phydev) if (err) phy_error(phydev); + free_irq(phydev->irq, phydev); + /* - * Finish any pending work; we might have been scheduled to be called - * from keventd ourselves, but cancel_work_sync() handles that. + * Cannot call flush_scheduled_work() here as desired because + * of rtnl_lock(), but we do not really care about what would + * be done, except from enable_irq(), so cancel any work + * possibly pending and take care of the matter below. */ cancel_work_sync(&phydev->phy_queue); - - free_irq(phydev->irq, phydev); + /* + * If work indeed has been cancelled, disable_irq() will have + * been left unbalanced from phy_interrupt() and enable_irq() + * has to be called so that other devices on the line work. + */ + while (atomic_dec_return(&phydev->irq_disable) >= 0) + enable_irq(phydev->irq); return err; } @@ -695,6 +707,7 @@ static void phy_change(struct work_struct *work) phydev->state = PHY_CHANGELINK; spin_unlock_bh(&phydev->lock); + atomic_dec(&phydev->irq_disable); enable_irq(phydev->irq); /* Reenable interrupts */ @@ -708,6 +721,7 @@ static void phy_change(struct work_struct *work) irq_enable_err: disable_irq(phydev->irq); + atomic_inc(&phydev->irq_disable); phy_err: phy_error(phydev); } diff --git a/include/linux/phy.h b/include/linux/phy.h index 2a659789f9ca..f0742b6aaa64 100644 --- a/include/linux/phy.h +++ b/include/linux/phy.h @@ -25,6 +25,8 @@ #include #include +#include + #define PHY_BASIC_FEATURES (SUPPORTED_10baseT_Half | \ SUPPORTED_10baseT_Full | \ SUPPORTED_100baseT_Half | \ @@ -281,6 +283,7 @@ struct phy_device { /* Interrupt and Polling infrastructure */ struct work_struct phy_queue; struct timer_list phy_timer; + atomic_t irq_disable; spinlock_t lock;