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Subject[patch 03/23] [PATCH] Fix soft lockup with ALSA rtc-timer
-stable review patch.  If anyone has any objections, please let us know.
------------------

Fixed the soft lockup of ALSA rtc-timer due to the wrong irq
handling in rtc_control(). The call of rtc_control() can be atomic.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/char/rtc.c | 65 ++++++++++++++++++++++++++++++-----------------------
1 file changed, 38 insertions(+), 27 deletions(-)

--- linux-2.6.14.2.orig/drivers/char/rtc.c
+++ linux-2.6.14.2/drivers/char/rtc.c
@@ -149,8 +149,22 @@ static void get_rtc_alm_time (struct rtc
#ifdef RTC_IRQ
static void rtc_dropped_irq(unsigned long data);

-static void set_rtc_irq_bit(unsigned char bit);
-static void mask_rtc_irq_bit(unsigned char bit);
+static void set_rtc_irq_bit_locked(unsigned char bit);
+static void mask_rtc_irq_bit_locked(unsigned char bit);
+
+static inline void set_rtc_irq_bit(unsigned char bit)
+{
+ spin_lock_irq(&rtc_lock);
+ set_rtc_irq_bit_locked(bit);
+ spin_unlock_irq(&rtc_lock);
+}
+
+static void mask_rtc_irq_bit(unsigned char bit)
+{
+ spin_lock_irq(&rtc_lock);
+ mask_rtc_irq_bit_locked(bit);
+ spin_unlock_irq(&rtc_lock);
+}
#endif

static int rtc_proc_open(struct inode *inode, struct file *file);
@@ -401,18 +415,19 @@ static int rtc_do_ioctl(unsigned int cmd
}
case RTC_PIE_OFF: /* Mask periodic int. enab. bit */
{
- mask_rtc_irq_bit(RTC_PIE);
+ unsigned long flags; /* can be called from isr via rtc_control() */
+ spin_lock_irqsave (&rtc_lock, flags);
+ mask_rtc_irq_bit_locked(RTC_PIE);
if (rtc_status & RTC_TIMER_ON) {
- spin_lock_irq (&rtc_lock);
rtc_status &= ~RTC_TIMER_ON;
del_timer(&rtc_irq_timer);
- spin_unlock_irq (&rtc_lock);
}
+ spin_unlock_irqrestore (&rtc_lock, flags);
return 0;
}
case RTC_PIE_ON: /* Allow periodic ints */
{
-
+ unsigned long flags; /* can be called from isr via rtc_control() */
/*
* We don't really want Joe User enabling more
* than 64Hz of interrupts on a multi-user machine.
@@ -421,14 +436,14 @@ static int rtc_do_ioctl(unsigned int cmd
(!capable(CAP_SYS_RESOURCE)))
return -EACCES;

+ spin_lock_irqsave (&rtc_lock, flags);
if (!(rtc_status & RTC_TIMER_ON)) {
- spin_lock_irq (&rtc_lock);
rtc_irq_timer.expires = jiffies + HZ/rtc_freq + 2*HZ/100;
add_timer(&rtc_irq_timer);
rtc_status |= RTC_TIMER_ON;
- spin_unlock_irq (&rtc_lock);
}
- set_rtc_irq_bit(RTC_PIE);
+ set_rtc_irq_bit_locked(RTC_PIE);
+ spin_unlock_irqrestore (&rtc_lock, flags);
return 0;
}
case RTC_UIE_OFF: /* Mask ints from RTC updates. */
@@ -609,6 +624,7 @@ static int rtc_do_ioctl(unsigned int cmd
{
int tmp = 0;
unsigned char val;
+ unsigned long flags; /* can be called from isr via rtc_control() */

/*
* The max we can do is 8192Hz.
@@ -631,9 +647,9 @@ static int rtc_do_ioctl(unsigned int cmd
if (arg != (1<<tmp))
return -EINVAL;

- spin_lock_irq(&rtc_lock);
+ spin_lock_irqsave(&rtc_lock, flags);
if (hpet_set_periodic_freq(arg)) {
- spin_unlock_irq(&rtc_lock);
+ spin_unlock_irqrestore(&rtc_lock, flags);
return 0;
}
rtc_freq = arg;
@@ -641,7 +657,7 @@ static int rtc_do_ioctl(unsigned int cmd
val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
val |= (16 - tmp);
CMOS_WRITE(val, RTC_FREQ_SELECT);
- spin_unlock_irq(&rtc_lock);
+ spin_unlock_irqrestore(&rtc_lock, flags);
return 0;
}
#endif
@@ -844,12 +860,15 @@ int rtc_control(rtc_task_t *task, unsign
#ifndef RTC_IRQ
return -EIO;
#else
- spin_lock_irq(&rtc_task_lock);
+ unsigned long flags;
+ if (cmd != RTC_PIE_ON && cmd != RTC_PIE_OFF && cmd != RTC_IRQP_SET)
+ return -EINVAL;
+ spin_lock_irqsave(&rtc_task_lock, flags);
if (rtc_callback != task) {
- spin_unlock_irq(&rtc_task_lock);
+ spin_unlock_irqrestore(&rtc_task_lock, flags);
return -ENXIO;
}
- spin_unlock_irq(&rtc_task_lock);
+ spin_unlock_irqrestore(&rtc_task_lock, flags);
return rtc_do_ioctl(cmd, arg, 1);
#endif
}
@@ -1306,40 +1325,32 @@ static void get_rtc_alm_time(struct rtc_
* meddles with the interrupt enable/disable bits.
*/

-static void mask_rtc_irq_bit(unsigned char bit)
+static void mask_rtc_irq_bit_locked(unsigned char bit)
{
unsigned char val;

- spin_lock_irq(&rtc_lock);
- if (hpet_mask_rtc_irq_bit(bit)) {
- spin_unlock_irq(&rtc_lock);
+ if (hpet_mask_rtc_irq_bit(bit))
return;
- }
val = CMOS_READ(RTC_CONTROL);
val &= ~bit;
CMOS_WRITE(val, RTC_CONTROL);
CMOS_READ(RTC_INTR_FLAGS);

rtc_irq_data = 0;
- spin_unlock_irq(&rtc_lock);
}

-static void set_rtc_irq_bit(unsigned char bit)
+static void set_rtc_irq_bit_locked(unsigned char bit)
{
unsigned char val;

- spin_lock_irq(&rtc_lock);
- if (hpet_set_rtc_irq_bit(bit)) {
- spin_unlock_irq(&rtc_lock);
+ if (hpet_set_rtc_irq_bit(bit))
return;
- }
val = CMOS_READ(RTC_CONTROL);
val |= bit;
CMOS_WRITE(val, RTC_CONTROL);
CMOS_READ(RTC_INTR_FLAGS);

rtc_irq_data = 0;
- spin_unlock_irq(&rtc_lock);
}
#endif

--
-
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