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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rtnl_mutex being held) has been replaced by cancel_work_sync() another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: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Andy Fleming <afleming@freescale.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This commit is contained in:
Maciej W. Rozycki 2007-09-28 22:42:14 -07:00 committed by David S. Miller
parent f7ab697d32
commit 0ac4952731
2 changed files with 22 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
drivers/net/phy/phy.c
View File

@ -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);
}

3
include/linux/phy.h
View File

@ -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;