Messages in this thread Patch in this message | | | Date | Mon, 25 Aug 2003 13:53:48 -0700 | From | Nick Pollitt <> | Subject | [PATCH] 2.4 avenrun values |
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In sysinfo there is a cli/sti around the reading of the avenrun values. On a UP system, this will prevent a timer tick/timer bh from coming in and updating the values while they're being read.
However, on an SMP system, using the cli on some cpu other than cpu0 will not stop the timer bh on cpu0 from updating the avenrun values while they're being read by sysinfo. Also, loadavg_read_proc does no locking whatsoever.
Below is a patch that uses the xtime_lock around the writer and both readers of the avenrun values. Please apply.
--- 1.21/fs/proc/proc_misc.c Mon Jul 14 13:10:30 2003 +++ edited/fs/proc/proc_misc.c Fri Aug 22 16:28:37 2003 @@ -65,6 +65,7 @@ #ifdef CONFIG_SGI_DS1286 extern int get_ds1286_status(char *); #endif +extern rwlock_t xtime_lock; void proc_sprintf(char *page, off_t *off, int *lenp, const char *format, ...) { @@ -101,17 +102,22 @@ static int loadavg_read_proc(char *page, char **start, off_t off, int count, int *eof, void *data) { - int a, b, c; + int a, b, c, d, e; int len; + read_lock(&xtime_lock); a = avenrun[0] + (FIXED_1/200); b = avenrun[1] + (FIXED_1/200); c = avenrun[2] + (FIXED_1/200); + d = nr_running; + e = nr_threads; + read_unlock(&xtime_lock); + len = sprintf(page,"%d.%02d %d.%02d %d.%02d %d/%d %d\n", LOAD_INT(a), LOAD_FRAC(a), LOAD_INT(b), LOAD_FRAC(b), LOAD_INT(c), LOAD_FRAC(c), - nr_running, nr_threads, last_pid); + d, e, last_pid); return proc_calc_metrics(page, start, off, count, eof, len); } --- 1.2/kernel/info.c Mon Feb 4 23:39:30 2002 +++ edited/kernel/info.c Fri Aug 22 16:19:12 2003 @@ -13,13 +13,15 @@ #include <asm/uaccess.h> +extern rwlock_t xtime_lock; + asmlinkage long sys_sysinfo(struct sysinfo *info) { struct sysinfo val; memset((char *)&val, 0, sizeof(struct sysinfo)); - cli(); + read_lock(&xtime_lock); val.uptime = jiffies / HZ; val.loads[0] = avenrun[0] << (SI_LOAD_SHIFT - FSHIFT); @@ -27,7 +29,7 @@ val.loads[2] = avenrun[2] << (SI_LOAD_SHIFT - FSHIFT); val.procs = nr_threads-1; - sti(); + read_unlock(&xtime_lock); si_meminfo(&val); si_swapinfo(&val); --- 1.7/kernel/timer.c Sun Oct 6 12:03:31 2002 +++ edited/kernel/timer.c Fri Aug 22 15:20:27 2003 @@ -686,8 +686,8 @@ update_wall_time(ticks); } vxtime_unlock(); - write_unlock_irq(&xtime_lock); calc_load(ticks); + write_unlock_irq(&xtime_lock); } void timer_bh(void) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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