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authorIngo Molnar <mingo@elte.hu>2008-08-23 11:59:07 -0400
committerIngo Molnar <mingo@elte.hu>2008-08-23 12:02:18 -0400
commit38c052f8cff1bd323ccfa968136a9556652ee420 (patch)
tree6cee3c0384438e13f065d196195a5d46a3941e4b /include/asm-generic
parent3c4fbe5e01d7e5309be5045e7ae0db20a049e6dc (diff)
rtc: fix deadlock
if get_rtc_time() is _ever_ called with IRQs off, we deadlock badly in it, waiting for jiffies to increment. So make the code more robust by doing an explicit mdelay(20). This solves a very hard to reproduce/debug hard lockup reported by Mikael Pettersson. Reported-by: Mikael Pettersson <mikpe@it.uu.se> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/rtc.h12
1 files changed, 4 insertions, 8 deletions
diff --git a/include/asm-generic/rtc.h b/include/asm-generic/rtc.h
index be4af0029ac..71ef3f0b968 100644
--- a/include/asm-generic/rtc.h
+++ b/include/asm-generic/rtc.h
@@ -15,6 +15,7 @@
15#include <linux/mc146818rtc.h> 15#include <linux/mc146818rtc.h>
16#include <linux/rtc.h> 16#include <linux/rtc.h>
17#include <linux/bcd.h> 17#include <linux/bcd.h>
18#include <linux/delay.h>
18 19
19#define RTC_PIE 0x40 /* periodic interrupt enable */ 20#define RTC_PIE 0x40 /* periodic interrupt enable */
20#define RTC_AIE 0x20 /* alarm interrupt enable */ 21#define RTC_AIE 0x20 /* alarm interrupt enable */
@@ -43,7 +44,6 @@ static inline unsigned char rtc_is_updating(void)
43 44
44static inline unsigned int get_rtc_time(struct rtc_time *time) 45static inline unsigned int get_rtc_time(struct rtc_time *time)
45{ 46{
46 unsigned long uip_watchdog = jiffies;
47 unsigned char ctrl; 47 unsigned char ctrl;
48 unsigned long flags; 48 unsigned long flags;
49 49
@@ -53,19 +53,15 @@ static inline unsigned int get_rtc_time(struct rtc_time *time)
53 53
54 /* 54 /*
55 * read RTC once any update in progress is done. The update 55 * read RTC once any update in progress is done. The update
56 * can take just over 2ms. We wait 10 to 20ms. There is no need to 56 * can take just over 2ms. We wait 20ms. There is no need to
57 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP. 57 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
58 * If you need to know *exactly* when a second has started, enable 58 * If you need to know *exactly* when a second has started, enable
59 * periodic update complete interrupts, (via ioctl) and then 59 * periodic update complete interrupts, (via ioctl) and then
60 * immediately read /dev/rtc which will block until you get the IRQ. 60 * immediately read /dev/rtc which will block until you get the IRQ.
61 * Once the read clears, read the RTC time (again via ioctl). Easy. 61 * Once the read clears, read the RTC time (again via ioctl). Easy.
62 */ 62 */
63 63 if (rtc_is_updating())
64 if (rtc_is_updating() != 0) 64 mdelay(20);
65 while (jiffies - uip_watchdog < 2*HZ/100) {
66 barrier();
67 cpu_relax();
68 }
69 65
70 /* 66 /*
71 * Only the values that we read from the RTC are set. We leave 67 * Only the values that we read from the RTC are set. We leave