| Message ID | 20170314092349.10981-8-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
Hi Nick, On Tue, Mar 14, 2017 at 07:23:48PM +1000, Nicholas Piggin wrote: > When taking the core idle state lock, grab it immediately like a > regular lock, rather than adding more tests in there. Holding the lock > keeps it stable, so there is no need to do it whole holding the > reservation. I agree with this patch. Just a minor query > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > --- > arch/powerpc/kernel/idle_book3s.S | 20 +++++++++++--------- > 1 file changed, 11 insertions(+), 9 deletions(-) > > diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S > index 1c91dc35c559..3cb75907c5c5 100644 > --- a/arch/powerpc/kernel/idle_book3s.S > +++ b/arch/powerpc/kernel/idle_book3s.S > @@ -488,12 +488,12 @@ BEGIN_FTR_SECTION > CHECK_HMI_INTERRUPT > END_FTR_SECTION_IFSET(CPU_FTR_HVMODE) > > - lbz r7,PACA_THREAD_MASK(r13) > ld r14,PACA_CORE_IDLE_STATE_PTR(r13) > -lwarx_loop2: > - lwarx r15,0,r14 > - andis. r9,r15,PNV_CORE_IDLE_LOCK_BIT@h > + lbz r7,PACA_THREAD_MASK(r13) Is reversing the order of loads into r7 and r14 intentional? Other than that, Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> > + > /* > + * Take the core lock to synchronize against other threads. > + * > * Lock bit is set in one of the 2 cases- > * a. In the sleep/winkle enter path, the last thread is executing > * fastsleep workaround code. > @@ -501,7 +501,14 @@ lwarx_loop2: > * workaround undo code or resyncing timebase or restoring context > * In either case loop until the lock bit is cleared. > */ > +1: > + lwarx r15,0,r14 > + andis. r9,r15,PNV_CORE_IDLE_LOCK_BIT@h > bnel- core_idle_lock_held > + oris r15,r15,PNV_CORE_IDLE_LOCK_BIT@h > + stwcx. r15,0,r14 > + bne- 1b > + isync > > andi. r9,r15,PNV_CORE_IDLE_THREAD_BITS > cmpwi cr2,r9,0 > @@ -513,11 +520,6 @@ lwarx_loop2: > * cr4 - gt or eq if waking up from complete hypervisor state loss. > */ > > - oris r15,r15,PNV_CORE_IDLE_LOCK_BIT@h > - stwcx. r15,0,r14 > - bne- lwarx_loop2 > - isync > - > BEGIN_FTR_SECTION > lbz r4,PACA_SUBCORE_SIBLING_MASK(r13) > and r4,r4,r15 > -- > 2.11.0 >
On Thu, 16 Mar 2017 18:13:28 +0530 Gautham R Shenoy <ego@linux.vnet.ibm.com> wrote: > Hi Nick, > > On Tue, Mar 14, 2017 at 07:23:48PM +1000, Nicholas Piggin wrote: > > When taking the core idle state lock, grab it immediately like a > > regular lock, rather than adding more tests in there. Holding the lock > > keeps it stable, so there is no need to do it whole holding the > > reservation. > > I agree with this patch. Just a minor query > > > > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > > --- > > arch/powerpc/kernel/idle_book3s.S | 20 +++++++++++--------- > > 1 file changed, 11 insertions(+), 9 deletions(-) > > > > diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S > > index 1c91dc35c559..3cb75907c5c5 100644 > > --- a/arch/powerpc/kernel/idle_book3s.S > > +++ b/arch/powerpc/kernel/idle_book3s.S > > @@ -488,12 +488,12 @@ BEGIN_FTR_SECTION > > CHECK_HMI_INTERRUPT > > END_FTR_SECTION_IFSET(CPU_FTR_HVMODE) > > > > - lbz r7,PACA_THREAD_MASK(r13) > > ld r14,PACA_CORE_IDLE_STATE_PTR(r13) > > -lwarx_loop2: > > - lwarx r15,0,r14 > > - andis. r9,r15,PNV_CORE_IDLE_LOCK_BIT@h > > + lbz r7,PACA_THREAD_MASK(r13) > > Is reversing the order of loads into r7 and r14 intentional? Oh, yes I guess it is because we use r14 result first. I should have mentioned it but I forgot about it. Probably they decode together, but you might get them in different cycles. Thanks for the review! Thanks, Nick
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index 1c91dc35c559..3cb75907c5c5 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -488,12 +488,12 @@ BEGIN_FTR_SECTION CHECK_HMI_INTERRUPT END_FTR_SECTION_IFSET(CPU_FTR_HVMODE) - lbz r7,PACA_THREAD_MASK(r13) ld r14,PACA_CORE_IDLE_STATE_PTR(r13) -lwarx_loop2: - lwarx r15,0,r14 - andis. r9,r15,PNV_CORE_IDLE_LOCK_BIT@h + lbz r7,PACA_THREAD_MASK(r13) + /* + * Take the core lock to synchronize against other threads. + * * Lock bit is set in one of the 2 cases- * a. In the sleep/winkle enter path, the last thread is executing * fastsleep workaround code. @@ -501,7 +501,14 @@ lwarx_loop2: * workaround undo code or resyncing timebase or restoring context * In either case loop until the lock bit is cleared. */ +1: + lwarx r15,0,r14 + andis. r9,r15,PNV_CORE_IDLE_LOCK_BIT@h bnel- core_idle_lock_held + oris r15,r15,PNV_CORE_IDLE_LOCK_BIT@h + stwcx. r15,0,r14 + bne- 1b + isync andi. r9,r15,PNV_CORE_IDLE_THREAD_BITS cmpwi cr2,r9,0 @@ -513,11 +520,6 @@ lwarx_loop2: * cr4 - gt or eq if waking up from complete hypervisor state loss. */ - oris r15,r15,PNV_CORE_IDLE_LOCK_BIT@h - stwcx. r15,0,r14 - bne- lwarx_loop2 - isync - BEGIN_FTR_SECTION lbz r4,PACA_SUBCORE_SIBLING_MASK(r13) and r4,r4,r15
When taking the core idle state lock, grab it immediately like a regular lock, rather than adding more tests in there. Holding the lock keeps it stable, so there is no need to do it whole holding the reservation. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/idle_book3s.S | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)