From 47997d756aa2a84ab577e1b0383cc12d582fc69c Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Wed, 21 Sep 2011 16:08:03 +0200 Subject: x86/rtc: Don't recursively acquire rtc_lock A deadlock was introduced on x86 in commit ef68c8f87ed1 ("x86: Serialize EFI time accesses on rtc_lock") because efi_get_time() and friends can be called with rtc_lock already held by read_persistent_time(), e.g.: timekeeping_init() read_persistent_clock() <-- acquire rtc_lock efi_get_time() phys_efi_get_time() <-- acquire rtc_lock To fix this let's push the locking down into the get_wallclock() and set_wallclock() implementations. Only the clock implementations that access the x86 RTC directly need to acquire rtc_lock, so it makes sense to push the locking down into the rtc, vrtc and efi code. The virtualization implementations don't require rtc_lock to be held because they provide their own serialization. Signed-off-by: Matt Fleming Acked-by: Jan Beulich Acked-by: Avi Kivity [for the virtualization aspect] Cc: "H. Peter Anvin" Cc: Zhang Rui Cc: Josh Boyer Signed-off-by: Andrew Morton Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/platform/mrst/vrtc.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/x86/platform') diff --git a/arch/x86/platform/mrst/vrtc.c b/arch/x86/platform/mrst/vrtc.c index 73d70d65e76e..6d5dbcdd444a 100644 --- a/arch/x86/platform/mrst/vrtc.c +++ b/arch/x86/platform/mrst/vrtc.c @@ -58,8 +58,11 @@ EXPORT_SYMBOL_GPL(vrtc_cmos_write); unsigned long vrtc_get_time(void) { u8 sec, min, hour, mday, mon; + unsigned long flags; u32 year; + spin_lock_irqsave(&rtc_lock, flags); + while ((vrtc_cmos_read(RTC_FREQ_SELECT) & RTC_UIP)) cpu_relax(); @@ -70,6 +73,8 @@ unsigned long vrtc_get_time(void) mon = vrtc_cmos_read(RTC_MONTH); year = vrtc_cmos_read(RTC_YEAR); + spin_unlock_irqrestore(&rtc_lock, flags); + /* vRTC YEAR reg contains the offset to 1960 */ year += 1960; @@ -83,8 +88,10 @@ unsigned long vrtc_get_time(void) int vrtc_set_mmss(unsigned long nowtime) { int real_sec, real_min; + unsigned long flags; int vrtc_min; + spin_lock_irqsave(&rtc_lock, flags); vrtc_min = vrtc_cmos_read(RTC_MINUTES); real_sec = nowtime % 60; @@ -95,6 +102,8 @@ int vrtc_set_mmss(unsigned long nowtime) vrtc_cmos_write(real_sec, RTC_SECONDS); vrtc_cmos_write(real_min, RTC_MINUTES); + spin_unlock_irqrestore(&rtc_lock, flags); + return 0; } -- cgit v1.2.3