On Wed, Dec 08, 2010 at 09:04:28AM +0100, Heiko Carstens wrote: > On Tue, Dec 07, 2010 at 04:45:07PM -0800, Greg KH wrote: > > 2.6.32-stable review patch. If anyone has any objections, please let us > > know. > > > > ------------------ > > > > From: Heiko Carstens <[email protected]> > > > > commit e8129c642155616d9e2160a75f103e127c8c3708 upstream. > > > > On each machine check all registers are revalidated. The save area for > > the clock comparator however only contains the upper most seven bytes > > of the former contents, if valid. > > Therefore the machine check handler uses a store clock instruction to > > get the current time and writes that to the clock comparator register > > which in turn will generate an immediate timer interrupt. > > However within the lowcore the expected time of the next timer > > interrupt is stored. If the interrupt happens before that time the > > handler won't be called. In turn the clock comparator won't be > > reprogrammed and therefore the interrupt condition stays pending which > > causes an interrupt loop until the expected time is reached. > > > > On NOHZ machines this can result in unresponsive machines since the > > time of the next expected interrupted can be a couple of days in the > > future. > > > > To fix this just revalidate the clock comparator register with the > > expected value. > > In addition the special handling for udelay must be changed as well. > > > > Signed-off-by: Heiko Carstens <[email protected]> > > Signed-off-by: Martin Schwidefsky <[email protected]> > > Signed-off-by: Greg Kroah-Hartman <[email protected]> > > [...] > > > --- > > arch/s390/kernel/nmi.c | 10 ++++------ > > arch/s390/lib/delay.c | 14 +++++++++----- > > 2 files changed, 13 insertions(+), 11 deletions(-) > > > > --- a/arch/s390/kernel/nmi.c > > +++ b/arch/s390/kernel/nmi.c > > @@ -95,7 +95,6 @@ EXPORT_SYMBOL_GPL(s390_handle_mcck); > > static int notrace s390_revalidate_registers(struct mci *mci) > > { > > int kill_task; > > - u64 tmpclock; > > u64 zero; > > void *fpt_save_area, *fpt_creg_save_area; > > > > @@ -214,11 +213,10 @@ static int notrace s390_revalidate_regis > > : "0", "cc"); > > #endif > > /* Revalidate clock comparator register */ > > - asm volatile( > > - " stck 0(%1)\n" > > - " sckc 0(%1)" > > - : "=m" (tmpclock) : "a" (&(tmpclock)) : "cc", "memory"); > > - > > + if (S390_lowcore.clock_comparator == -1) > > + set_clock_comparator(S390_lowcore.mcck_clock); > ^^^ > This line won't compile on 2.6.32. That's why I sent a slightly different > patch to -stable (and also the reason why I removed Martin's Sign-off) ;)
Ah, please be more clear that you are sending a modifed version for me to apply instead of taking the upstream patch directly, which is the default for me to do so in order to make sure nothing is incorrect. > > Here is the version I sent to [email protected] again: > > Subject: [S390] nmi: fix clock comparator revalidation I'll go replace the version I had with this one. thanks, greg k-h _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
