From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH] xen/x86: Be more power-efficient when waiting forever Date: Mon, 02 Dec 2013 15:23:59 +0000 Message-ID: References: <1385995089-440-1-git-send-email-andrew.cooper3@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1385995089-440-1-git-send-email-andrew.cooper3@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper , Xen-devel Cc: George Dunlap , Jan Beulich List-Id: xen-devel@lists.xenproject.org On 02/12/2013 14:38, "Andrew Cooper" wrote: > The effect is unchanged, but the processor will be spending most of its time > in the C1 or C1E power state rather than C0. > > Signed-off-by: Andrew Cooper > CC: Keir Fraser > CC: Jan Beulich > CC: George Dunlap Acked-by: Keir Fraser > --- > > This was discovered while I was playing about in the early_page_fault() > handler with the IBM box which was corruption the Xen code section. > > There is one final for(;;); loop, but is in common code and immediately > following a call to panic(), so is actually dead code and will be cleaned up > in v2 of my "noreturn" series at the start of 4.5 > > George: I am requesting that this get a freeze exception, under the > qualification of #2 "An awesome release", given no function change threatening > --- > xen/arch/x86/efi/boot.c | 3 ++- > xen/arch/x86/traps.c | 3 ++- > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/x86/efi/boot.c b/xen/arch/x86/efi/boot.c > index 0dd935c..602cc12 100644 > --- a/xen/arch/x86/efi/boot.c > +++ b/xen/arch/x86/efi/boot.c > @@ -201,7 +201,8 @@ static void __init __attribute__((__noreturn__)) > blexit(const CHAR16 *str) > efi_bs->FreePages(xsm.addr, PFN_UP(xsm.size)); > > efi_bs->Exit(efi_ih, EFI_SUCCESS, 0, NULL); > - for( ; ; ); /* not reached */ > + for ( ; ; ) /* not reached */ > + halt(); > } > > /* generic routine for printing error messages */ > diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c > index d8b3eac..8c355e5 100644 > --- a/xen/arch/x86/traps.c > +++ b/xen/arch/x86/traps.c > @@ -1448,7 +1448,8 @@ void __init do_early_page_fault(struct cpu_user_regs > *regs) > printk("Stack dump: "); > while ( ((long)stk & ((PAGE_SIZE - 1) & ~(BYTES_PER_LONG - 1))) != 0 > ) > printk("%p ", _p(*stk++)); > - for ( ; ; ) ; > + for ( ; ; ) > + halt(); > } > } >