Re: 2.6.12-rc2-mm3

Ed Tomlinson
2005-04-14T00:39:05Z

On Wednesday 13 April 2005 20:20, Andrew Morton wrote:
> Ed Tomlinson <tomlins@cam.org> wrote:
> >
> > > Don't think so - it works OK here. Checked the .config? Does the serial
> > > port work if you do `echo foo > /dev/ttyS0'? ACPI?
> >
> > Turned out it was some old ups software that got reactivated on the box displaying the
> > console - was a pain to disable it....
>
> OK.
>
> > In any case, when the box reboots there are not any messages. Any ideas on what debug
> > options to enable or suggestions on how we can figure out the cause of the reboots.
>
> There were a few problems in the task switching area - maybe that.

These hit arch/i386. Are they going to help on an x86_64 box?

Ed

> From: Ingo Molnar <mingo@elte.hu>
>
> delay the reloading of segment registers into switch_mm(), so that if
> the LDT size changes we dont get a (silent) fault and a zeroed selector
> register upon reloading.
>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> ---
>
> 25-akpm/arch/i386/kernel/process.c | 10 +++++-----
> 25-akpm/include/asm-i386/mmu_context.h | 7 +++++++
> 2 files changed, 12 insertions(+), 5 deletions(-)
>
> diff -puN arch/i386/kernel/process.c~sched-unlocked-context-switches-fix arch/i386/kernel/process.c
> --- 25/arch/i386/kernel/process.c~sched-unlocked-context-switches-fix 2005-04-12 03:43:07.254363568 -0700
> +++ 25-akpm/arch/i386/kernel/process.c 2005-04-12 03:43:07.259362808 -0700
> @@ -653,12 +653,12 @@ struct task_struct fastcall * __switch_t
> asm volatile("mov %%gs,%0":"=m" (prev->gs));
>
> /*
> - * Restore %fs and %gs if needed.
> + * Clear selectors if needed:
> */
> - if (unlikely(prev->fs | prev->gs | next->fs | next->gs)) {
> - loadsegment(fs, next->fs);
> - loadsegment(gs, next->gs);
> - }
> + if (unlikely((prev->fs | prev->gs) && !(next->fs | next->gs))) {
> + loadsegment(fs, next->fs);
> + loadsegment(gs, next->gs);
> + }
>
> /*
> * Now maybe reload the debug registers
> diff -puN include/asm-i386/mmu_context.h~sched-unlocked-context-switches-fix include/asm-i386/mmu_context.h
> --- 25/include/asm-i386/mmu_context.h~sched-unlocked-context-switches-fix 2005-04-12 03:43:07.256363264 -0700
> +++ 25-akpm/include/asm-i386/mmu_context.h 2005-04-12 03:43:07.260362656 -0700
> @@ -61,6 +61,13 @@ static inline void switch_mm(struct mm_s
> }
> }
> #endif
> + /*
> + * Now that we've switched the LDT, load segments:
> + */
> + if (unlikely(current->thread.fs | current->thread.gs)) {
> + loadsegment(fs, current->thread.fs);
> + loadsegment(gs, current->thread.gs);
> + }
> }
>
> #define deactivate_mm(tsk, mm) \
> _
>
>