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Code Issues Releases Activity

Partial fix for a bug in rev.1.231. If suspend/resume clobbers the

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RTC state, then it may clobber the RTC index register, so the index
register must be restored before using it to restore control registers
in rtc_restore().

The following problems remain:
- rtc_restore() is only called if pmtimer is configured.  Buggy
  suspend/resumes are more likely to clobber the index register than
  a control register, so pmtimer is more needed than it used to be.
- pmtimer doesn't exist for amd64.
- Restoring of the RTC state may race with rtcintr().  If an RTC
  interrupt is handled before the state is restored, then rtcin(RTC_INTR)
  in rtcintr() may read from the wrong register, so rtcintr() may spin
  forever.  This may be mitigated by the most common state clobbering
  being to turn off RTC interrupts.
This commit is contained in:
Bruce Evans 2007-03-05 09:10:17 +00:00
parent 9622f4d439
commit d78180f8f5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=167221
2 changed files with 2 additions and 0 deletions
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1
sys/i386/isa/clock.c
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@ -579,6 +579,7 @@ rtc_restore(void)
/* Restore all of the RTC's "status" (actually, control) registers. */
/* XXX locking is needed for RTC access. */
rtc_reg = -1;
writertc(RTC_STATUSB, RTCSB_24HR);
writertc(RTC_STATUSA, rtc_statusa);
writertc(RTC_STATUSB, rtc_statusb);

1
sys/isa/atrtc.c
View File

@ -579,6 +579,7 @@ rtc_restore(void)
/* Restore all of the RTC's "status" (actually, control) registers. */
/* XXX locking is needed for RTC access. */
rtc_reg = -1;
writertc(RTC_STATUSB, RTCSB_24HR);
writertc(RTC_STATUSA, rtc_statusa);
writertc(RTC_STATUSB, rtc_statusb);