| From | Vineet Gupta <> | Subject | Re: [PATCH 3.14 27/83] ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe | Date | Mon, 12 May 2014 04:54:56 +0000 |
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On Monday 12 May 2014 12:51 AM, Greg Kroah-Hartman wrote: > 3.14-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Vineet Gupta <Vineet.Gupta1@synopsys.com> > > commit 8aa9e85adac609588eeec356e5a85059b3b819ba upstream.
Hi Greg,
This one was also marked for stable 3.10 however because the 2 pre-req patches were not in yet, applying it would have failed and AFAIKR I did describe the state of things in that failure report. Anyhow can you please queue this one up for the next 3.10 stable.
Thx, -Vineet
> > There was a very small race window where resume to kernel mode from a > Exception Path (or pure kernel mode which is true for most of ARC > exceptions anyways), was not disabling interrupts in restore_regs, > clobbering the exception regs > > Anton found the culprit call flow (after many sleepless nights) > > | 1. we got a Trap from user land > | 2. started to service it. > | 3. While doing some stuff on user-land memory (I think it is padzero()), > | we got a DataTlbMiss > | 4. On return from it we are taking "resume_kernel_mode" path > | 5. NEED_RESHED is not set, so we go to "return from exception" path in > | restore regs. > | 6. there seems to be IRQ happening > > Signed-off-by: Vineet Gupta <vgupta@synopsys.com> > Cc: Anton Kolesov <Anton.Kolesov@synopsys.com> > Cc: Francois Bedard <Francois.Bedard@synopsys.com> > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > arch/arc/kernel/entry.S | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > --- a/arch/arc/kernel/entry.S > +++ b/arch/arc/kernel/entry.S > @@ -614,11 +614,13 @@ resume_user_mode_begin: > > resume_kernel_mode: > > -#ifdef CONFIG_PREEMPT > - > - ; This is a must for preempt_schedule_irq() > + ; Disable Interrupts from this point on > + ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq() > + ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe > IRQ_DISABLE r9 > > +#ifdef CONFIG_PREEMPT > + > ; Can't preempt if preemption disabled > GET_CURR_THR_INFO_FROM_SP r10 > ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] > > >
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