The patch titled Subject: x86 rtc: don't recursively acquire rtc_lock has been removed from the -mm tree. Its filename was x86-rtc-dont-recursively-acquire-rtc_lock.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ From: Matt Fleming <matt.fleming@xxxxxxxxx> 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 <DEADLOCK> 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 <matt.fleming@xxxxxxxxx> Acked-by: Jan Beulich <jbeulich@xxxxxxxxxx> Acked-by: Avi Kivity <avi@xxxxxxxxxx> [for the virtualization aspect] Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Zhang Rui <rui.zhang@xxxxxxxxx> Cc: Josh Boyer <jwboyer@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/rtc.c | 23 ++++++++++++----------- arch/x86/platform/mrst/vrtc.c | 9 +++++++++ 2 files changed, 21 insertions(+), 11 deletions(-) diff -puN arch/x86/kernel/rtc.c~x86-rtc-dont-recursively-acquire-rtc_lock arch/x86/kernel/rtc.c --- a/arch/x86/kernel/rtc.c~x86-rtc-dont-recursively-acquire-rtc_lock +++ a/arch/x86/kernel/rtc.c @@ -43,8 +43,11 @@ int mach_set_rtc_mmss(unsigned long nowt { int real_seconds, real_minutes, cmos_minutes; unsigned char save_control, save_freq_select; + unsigned long flags; int retval = 0; + spin_lock_irqsave(&rtc_lock, flags); + /* tell the clock it's being set */ save_control = CMOS_READ(RTC_CONTROL); CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); @@ -94,12 +97,17 @@ int mach_set_rtc_mmss(unsigned long nowt CMOS_WRITE(save_control, RTC_CONTROL); CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); + spin_unlock_irqrestore(&rtc_lock, flags); + return retval; } unsigned long mach_get_cmos_time(void) { unsigned int status, year, mon, day, hour, min, sec, century = 0; + unsigned long flags; + + spin_lock_irqsave(&rtc_lock, flags); /* * If UIP is clear, then we have >= 244 microseconds before @@ -126,6 +134,8 @@ unsigned long mach_get_cmos_time(void) status = CMOS_READ(RTC_CONTROL); WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY)); + spin_unlock_irqrestore(&rtc_lock, flags); + if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) { sec = bcd2bin(sec); min = bcd2bin(min); @@ -170,24 +180,15 @@ EXPORT_SYMBOL(rtc_cmos_write); int update_persistent_clock(struct timespec now) { - unsigned long flags; - int retval; - - spin_lock_irqsave(&rtc_lock, flags); - retval = x86_platform.set_wallclock(now.tv_sec); - spin_unlock_irqrestore(&rtc_lock, flags); - - return retval; + return x86_platform.set_wallclock(now.tv_sec); } /* not static: needed by APM */ void read_persistent_clock(struct timespec *ts) { - unsigned long retval, flags; + unsigned long retval; - spin_lock_irqsave(&rtc_lock, flags); retval = x86_platform.get_wallclock(); - spin_unlock_irqrestore(&rtc_lock, flags); ts->tv_sec = retval; ts->tv_nsec = 0; diff -puN arch/x86/platform/mrst/vrtc.c~x86-rtc-dont-recursively-acquire-rtc_lock arch/x86/platform/mrst/vrtc.c --- a/arch/x86/platform/mrst/vrtc.c~x86-rtc-dont-recursively-acquire-rtc_lock +++ a/arch/x86/platform/mrst/vrtc.c @@ -59,8 +59,11 @@ 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(); @@ -71,6 +74,8 @@ 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; @@ -84,8 +89,10 @@ 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; @@ -96,6 +103,8 @@ 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; } _ Patches currently in -mm which might be from matt.fleming@xxxxxxxxx are origin.patch linux-next.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html