On Wednesday 07 May 2014 06:57 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > The patch below does not apply to the 3.10-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to <stable@xxxxxxxxxxxxxxx>. > > thanks, > > greg k-h Hi Greg, This patch should now apply cleanly to 3.10 - given that you've added the 2 prerequisites patch(es) already per a seperate email. Thx, -Vineet > > ------------------ original commit in Linus's tree ------------------ > > From 8aa9e85adac609588eeec356e5a85059b3b819ba Mon Sep 17 00:00:00 2001 > From: Vineet Gupta <Vineet.Gupta1@xxxxxxxxxxxx> > Date: Wed, 30 Apr 2014 15:26:45 +0530 > Subject: [PATCH] ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe > > 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@xxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> #3.10, 3.12, 3.13, 3.14 > Cc: Anton Kolesov <Anton.Kolesov@xxxxxxxxxxxx> > Cc: Francois Bedard <Francois.Bedard@xxxxxxxxxxxx> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S > index 819dd5f7eb05..29b82adbf0b4 100644 > --- 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] > > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html