From: Ingo Molnar Date: Sat, 23 Aug 2008 15:59:07 +0000 (+0200) Subject: rtc: fix deadlock X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=38c052f8cff1bd323ccfa968136a9556652ee420;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git 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 Signed-off-by: Ingo Molnar --- diff --git a/include/asm-generic/rtc.h b/include/asm-generic/rtc.h index be4af0029ac0..71ef3f0b9685 100644 --- a/include/asm-generic/rtc.h +++ b/include/asm-generic/rtc.h @@ -15,6 +15,7 @@ #include #include #include +#include #define RTC_PIE 0x40 /* periodic interrupt enable */ #define RTC_AIE 0x20 /* alarm interrupt enable */ @@ -43,7 +44,6 @@ static inline unsigned char rtc_is_updating(void) static inline unsigned int get_rtc_time(struct rtc_time *time) { - unsigned long uip_watchdog = jiffies; unsigned char ctrl; unsigned long flags; @@ -53,19 +53,15 @@ static inline unsigned int get_rtc_time(struct rtc_time *time) /* * read RTC once any update in progress is done. The update - * can take just over 2ms. We wait 10 to 20ms. There is no need to + * can take just over 2ms. We wait 20ms. There is no need to * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP. * If you need to know *exactly* when a second has started, enable * periodic update complete interrupts, (via ioctl) and then * immediately read /dev/rtc which will block until you get the IRQ. * Once the read clears, read the RTC time (again via ioctl). Easy. */ - - if (rtc_is_updating() != 0) - while (jiffies - uip_watchdog < 2*HZ/100) { - barrier(); - cpu_relax(); - } + if (rtc_is_updating()) + mdelay(20); /* * Only the values that we read from the RTC are set. We leave