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Commit 0ac49527 authored by Maciej W. Rozycki's avatar Maciej W. Rozycki Committed by David S. Miller
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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rtnl_mutex being held) has been replaced by cancel_work_sync() another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: default avatarMaciej W. Rozycki <macro@linux-mips.org>
Cc: Andy Fleming <afleming@freescale.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJeff Garzik <jeff@garzik.org>
parent f7ab697d

drivers/net/phy/phy.c

+19 −5
Original line number Diff line number Diff line
@@ -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 <linux/timer.h>

#include <linux/workqueue.h>



#include <asm/atomic.h>

#include <asm/io.h>

#include <asm/irq.h>

#include <asm/uaccess.h>
@@ -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);

}

include/linux/phy.h

+3 −0
Original line number Diff line number Diff line
@@ -25,6 +25,8 @@ 
#include <linux/timer.h>

#include <linux/workqueue.h>



#include <asm/atomic.h>



#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;