Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0

[Ingo Molnar]

* K.R. Foley <kr@xxxxxxxxxx> wrote:

> Running amlat still hard locks the system. The last time this happened
> I got this in the log:
> 
>  Oct 26 21:43:56 porky kernel: BUG: sleeping function called from 
> invalid context amlat(3963) at kernel/mutex.c:28
> Oct 26 21:43:56 porky kernel: in_atomic():1 [00000001], irqs_disabled():1
> Oct 26 21:43:56 porky kernel:  [<c011c7da>] __might_sleep+0xca/0xe0 (12)
> Oct 26 21:43:56 porky kernel:  [<c0137d89>] _mutex_lock+0x39/0x50 (36)
> Oct 26 21:43:56 porky kernel:  [<c0137df6>]  _mutex_lock_irqsave+0x16/0x20 (24)
> Oct 26 21:43:56 porky kernel:  [<c012977d>] __mod_timer+0x4d/0x1f0 (12)
> Oct 26 21:43:56 porky kernel:  [<c01f6535>] rtc_do_ioctl+0x185/0x970 (44)

does the quick hack below help?

	Ingo

--- linux/drivers/char/rtc.c.orig
+++ linux/drivers/char/rtc.c
@@ -238,11 +238,11 @@ irqreturn_t rtc_interrupt(int irq, void 
 		rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);
 	}
 
+	spin_unlock (&rtc_lock);
+
 	if (rtc_status & RTC_TIMER_ON)
 		mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
 
-	spin_unlock (&rtc_lock);
-
 	/* Now do the rest of the actions */
 	spin_lock(&rtc_task_lock);
 	if (rtc_callback)
@@ -1094,10 +1094,6 @@ static void rtc_dropped_irq(unsigned lon
 		return;
 	}
 
-	/* Just in case someone disabled the timer from behind our back... */
-	if (rtc_status & RTC_TIMER_ON)
-		mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
-
 	rtc_irq_data += ((rtc_freq/HZ)<<8);
 	rtc_irq_data &= ~0xff;
 	rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);	/* restart */
@@ -1106,6 +1102,10 @@ static void rtc_dropped_irq(unsigned lon
 
 	spin_unlock_irq(&rtc_lock);
 
+	/* Just in case someone disabled the timer from behind our back... */
+	if (rtc_status & RTC_TIMER_ON)
+		mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
+
 	printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n", freq);
 
 	/* Now we have new data */
-
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