[PATCH][BUGFIX] Bug in timer_tsc cpufreq callback

[Pallipadi, Venkatesh]

Hi,

There is a bug in cpufreq call back funtion in timer_tsc routines,
that can result in system deadlock. The issue is: grabbing the
write_lock on xtime_lock without disabling the interrupts. So, 
if we happen to get a timer interrupt while we are in this code,
system will go into a deadlock.

This bug only effects the kernels that have CONFIG_CPU_FREQ enabled.
Attached patch fixes it. Please apply.


Thanks,
-Venkatesh


--- linux-2.6.0-test6/arch/i386/kernel/timers/timer_tsc.c.org
2003-10-10 14:01:02.000000000 -0700
+++ linux-2.6.0-test6/arch/i386/kernel/timers/timer_tsc.c
2003-10-10 14:01:24.000000000 -0700
@@ -321,7 +321,7 @@ time_cpufreq_notifier(struct notifier_bl
 {
 	struct cpufreq_freqs *freq = data;
 
-	write_seqlock(&xtime_lock);
+	write_seqlock_irq(&xtime_lock);
 	if (!ref_freq) {
 		ref_freq = freq->old;
 		loops_per_jiffy_ref =
cpu_data[freq->cpu].loops_per_jiffy;
@@ -342,7 +342,7 @@ time_cpufreq_notifier(struct notifier_bl
 		}
 #endif
 	}
-	write_sequnlock(&xtime_lock);
+	write_sequnlock_irq(&xtime_lock);
 
 	return 0;
 }

Attachment: tsc-deadlock.patch
Description: tsc-deadlock.patch