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author | Matt Fleming <matt.fleming@intel.com> | 2011-09-21 16:08:03 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2011-09-21 16:16:09 +0200 |
commit | 47997d756aa2a84ab577e1b0383cc12d582fc69c (patch) | |
tree | 9b5874e94a14f771a3e482fa09e1fc68785a9277 /arch/x86/kernel/rtc.c | |
parent | 9d037a777695993ec7437e5f451647dea7919d4c (diff) | |
download | linux-stable-47997d756aa2a84ab577e1b0383cc12d582fc69c.tar.gz linux-stable-47997d756aa2a84ab577e1b0383cc12d582fc69c.tar.bz2 linux-stable-47997d756aa2a84ab577e1b0383cc12d582fc69c.zip |
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@intel.com>
Acked-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Avi Kivity <avi@redhat.com> [for the virtualization aspect]
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Josh Boyer <jwboyer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/rtc.c')
-rw-r--r-- | arch/x86/kernel/rtc.c | 23 |
1 files changed, 12 insertions, 11 deletions
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c index 3f2ad2640d85..ccdbc16b8941 100644 --- a/arch/x86/kernel/rtc.c +++ b/arch/x86/kernel/rtc.c @@ -42,8 +42,11 @@ int mach_set_rtc_mmss(unsigned long nowtime) { 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); @@ -93,12 +96,17 @@ int mach_set_rtc_mmss(unsigned long nowtime) 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 @@ -125,6 +133,8 @@ 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); @@ -169,24 +179,15 @@ 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; |