Hi Kevin, Stuart ,
Woohooo You guys spotted !.
http://git.linux-mips.org/?p=linux.git;a=commit;h=d5ec6e3c seems to be
Once I restored previous version of stackframe.h 2.6.33-stable started
On Fri, 2010-12-24 at 04:32 -0800, Kevin D. Kissell wrote:
> Thank you, Stuart! I've spotted some definite breakage to SMTC between
> those versions. In arch/mips/include/asm/stackframe.h, someone moved
> the store of the Status register value in SAVE_SOME (line 169 or 204,
> depending on the version) from two instructions after the mfc0 to a
> point after the #ifdef for SMTC, presumably to get better pipelining of
> the register access. Unfortunately, the v1 register is also used in the
> SMTC-specific fragment to save TCStatus, so the Status value gets
> clobbered before it gets stored. This will eventually result in the
> Status register getting a TCStatus value, which has some bits on common,
> but isn't identical and sooner or later Bad Things will happen.
> I'm a little surprised this wasn't caught by visual inspection of the patch.
> Possible solutions would include reverting the store of the CP0_STATUS
> value to the block above the #ifdef, or, to retain whatever performance
> advantage was obtained by moving the store downward, to use v0/$2
> instead of v1/$3, as the staging register for the TCStatus value. I'd
> lean toward the second option, but I'm not in a position to test and
> submit a patch just now.
> Kevin K.
> On 12/23/10 1:09 PM, STUART VENTERS wrote:
> > Kevin,
> > I'm not sure if it's useful,
> > but finally I got the time to look at the two kernel versions Anoop
> > pointed out.
> > works 2.6.32-stable with patch 804
> > works_not 2.6.33-stable
> > greping for files with CONFIG_MIPS_MT_SMTC
> > and looking for timer interrupt related stuff found the following
> > differences:
> > arch/mips/include/asm/irq.h
> > arch/mips/kernel/irq.c
> > do_IRQ
> > arch/mips/include/asm/stackframe.h
> > SAVE_SOME SAVE_TEMP get/set_saved_sp
> > arch/mips/include/asm/time.h
> > clocksource_set_clock
> > arch/mips/kernel/process.c
> > cpu_idle
> > arch/mips/kernel/smtc.c
> > __irq_entry
> > ipi_decode
> > SMTC_CLOCK_TICK
> > Enclosed are the two subsets of files for a more expert look.
> > I'll try to look in more detail after Christmas.
> > Cheers,
> > Stuart