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authorMatt Fleming <matt.fleming@intel.com>2011-09-21 16:08:03 +0200
committerIngo Molnar <mingo@elte.hu>2011-09-21 16:16:09 +0200
commit47997d756aa2a84ab577e1b0383cc12d582fc69c (patch)
tree9b5874e94a14f771a3e482fa09e1fc68785a9277 /arch
parent9d037a777695993ec7437e5f451647dea7919d4c (diff)
downloadlinux-47997d756aa2a84ab577e1b0383cc12d582fc69c.tar.gz
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')
-rw-r--r--arch/x86/kernel/rtc.c23
-rw-r--r--arch/x86/platform/mrst/vrtc.c9
2 files changed, 21 insertions, 11 deletions
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 3f2ad2640d8..ccdbc16b894 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;
diff --git a/arch/x86/platform/mrst/vrtc.c b/arch/x86/platform/mrst/vrtc.c
index 73d70d65e76..6d5dbcdd444 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;
}