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| author | Yury Polyanskiy <ypolyans@princeton.edu> | 2010-05-25 01:33:02 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-25 19:07:02 +0400 |
| commit | 940370fc86b920b51a34217a1facc3e9e97c2456 (patch) | |
| tree | 6d53529bc158408c42df40d78ee728adb399f787 | |
| parent | b3b77c8caef1750ebeea1054e39e358550ea9f55 (diff) | |
| download | linux-940370fc86b920b51a34217a1facc3e9e97c2456.tar.xz | |
hangcheck-timer: fix x86_32 bugs
drivers/char/hangcheck-timer.c is doubly broken. When the overflown value
of TIMER_FREQ is abnormally low, it spams the syslog with KERN_CRIT
messages "Hangcheck: hangcheck value past margin!" But whether it happens
or not depends on HZ and lpj in a complex way. People have hit it
occasionally as far as google search can tell.
First, the following line overflows unsigned long:
# define TIMER_FREQ (HZ*loops_per_jiffy)
Second, and more importantly, loops_per_jiffy has little to do with the
con= version from the the time scale of get_cycles() (aka rdtsc) to the
time scale of jiffies.
The attached patch resolves both of the problems.
Acked-by: Joel Becker <joel.becker@oracle.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Jan Glauber <jan.glauber@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | drivers/char/hangcheck-timer.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/drivers/char/hangcheck-timer.c b/drivers/char/hangcheck-timer.c index 712d9f271aa6..e0249722d25f 100644 --- a/drivers/char/hangcheck-timer.c +++ b/drivers/char/hangcheck-timer.c @@ -49,8 +49,9 @@ #include <asm/uaccess.h> #include <linux/sysrq.h> #include <linux/timer.h> +#include <linux/time.h> -#define VERSION_STR "0.9.0" +#define VERSION_STR "0.9.1" #define DEFAULT_IOFENCE_MARGIN 60 /* Default fudge factor, in seconds */ #define DEFAULT_IOFENCE_TICK 180 /* Default timer timeout, in seconds */ @@ -119,10 +120,8 @@ __setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks); #if defined(CONFIG_S390) # define HAVE_MONOTONIC # define TIMER_FREQ 1000000000ULL -#elif defined(CONFIG_IA64) -# define TIMER_FREQ ((unsigned long long)local_cpu_data->itc_freq) #else -# define TIMER_FREQ (HZ*loops_per_jiffy) +# define TIMER_FREQ 1000000000ULL #endif #ifdef HAVE_MONOTONIC @@ -130,7 +129,9 @@ extern unsigned long long monotonic_clock(void); #else static inline unsigned long long monotonic_clock(void) { - return get_cycles(); + struct timespec ts; + getrawmonotonic(&ts); + return timespec_to_ns(&ts); } #endif /* HAVE_MONOTONIC */ @@ -168,6 +169,13 @@ static void hangcheck_fire(unsigned long data) printk(KERN_CRIT "Hangcheck: hangcheck value past margin!\n"); } } +#if 0 + /* + * Enable to investigate delays in detail + */ + printk("Hangcheck: called %Ld ns since last time (%Ld ns overshoot)\n", + tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ); +#endif mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ)); hangcheck_tsc = monotonic_clock(); } @@ -180,7 +188,7 @@ static int __init hangcheck_init(void) #if defined (HAVE_MONOTONIC) printk("Hangcheck: Using monotonic_clock().\n"); #else - printk("Hangcheck: Using get_cycles().\n"); + printk("Hangcheck: Using getrawmonotonic().\n"); #endif /* HAVE_MONOTONIC */ hangcheck_tsc_margin = (unsigned long long)(hangcheck_margin + hangcheck_tick); |