From 403fe5ae57c831968c3dbbaba291ae825a1c5aaa Mon Sep 17 00:00:00 2001 From: Petr Vandrovec Date: Fri, 5 Aug 2005 15:50:07 +0200 Subject: [PATCH] rtc: msleep() cannot be used from interrupt Since the beginning of July my Opteron box was randomly crashing and being rebooted by hardware watchdog. Today it finally did it in front of me, and this patch will hopefully fix it. The problem is that at the end of June (the 28th, to be exact: commit 47f176fdaf8924bc83fddcf9658f2fd3ef60d573, "[PATCH] Using msleep() instead of HZ") rtc_get_rtc_time was converted to use msleep() instead of busy waiting. But rtc_get_rtc_time is used by hpet_rtc_interrupt, and scheduling is not allowed during interrupt. So I'm reverting this part of original change, replacing msleep() back with busy loop. The original code was busy waiting for up to 20ms, but on my hardware in the worst case update-in-progress bit was asserted for at most 363 passes through loop (on 2GHz dual Opteron), much less than even one jiffie, not even talking about 20ms. So I changed code to just wait only as long as necessary. Otherwise when RTC was set to generate 8192Hz timer, it stopped doing anything for 20ms (160 pulses were skipped!) from time to time, and this is rather suboptimal as far as I can tell. Signed-off-by: Petr Vandrovec Signed-off-by: Linus Torvalds --- drivers/char/rtc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'drivers/char/rtc.c') diff --git a/drivers/char/rtc.c b/drivers/char/rtc.c index d8f9e94ae47..cd4fe8b1709 100644 --- a/drivers/char/rtc.c +++ b/drivers/char/rtc.c @@ -1209,6 +1209,7 @@ static int rtc_proc_open(struct inode *inode, struct file *file) void rtc_get_rtc_time(struct rtc_time *rtc_tm) { + unsigned long uip_watchdog = jiffies; unsigned char ctrl; #ifdef CONFIG_MACH_DECSTATION unsigned int real_year; @@ -1224,8 +1225,10 @@ void rtc_get_rtc_time(struct rtc_time *rtc_tm) * Once the read clears, read the RTC time (again via ioctl). Easy. */ - if (rtc_is_updating() != 0) - msleep(20); + while (rtc_is_updating() != 0 && jiffies - uip_watchdog < 2*HZ/100) { + barrier(); + cpu_relax(); + } /* * Only the values that we read from the RTC are set. We leave -- cgit v1.2.3