From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964810AbcI3FxR (ORCPT ); Fri, 30 Sep 2016 01:53:17 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:34737 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934349AbcI3FxH (ORCPT ); Fri, 30 Sep 2016 01:53:07 -0400 Date: Fri, 30 Sep 2016 13:52:44 +0800 From: Boqun Feng To: Pan Xinhui Cc: Christian Borntraeger , Peter Zijlstra , Martin Schwidefsky , Heiko Carstens , Pan Xinhui , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, xen-devel-request@lists.xenproject.org, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, mingo@redhat.com, paulmck@linux.vnet.ibm.com, will.deacon@arm.com, kernellwp@gmail.com, jgross@suse.com, pbonzini@redhat.com, bsingharora@gmail.com Subject: Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Message-ID: <20160930055236.GB22004@tardis.cn.ibm.com> References: <1475164265-246160-1-git-send-email-borntraeger@de.ibm.com> <1475164265-246160-2-git-send-email-borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ALfTUftag+2gvp1h" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.0 (2016-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ALfTUftag+2gvp1h Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 30, 2016 at 12:49:52PM +0800, Pan Xinhui wrote: >=20 >=20 > =E5=9C=A8 2016/9/29 23:51, Christian Borntraeger =E5=86=99=E9=81=93: > > this implements the s390 backend for commit > > "kernel/sched: introduce vcpu preempted check interface" > > by reworking the existing smp_vcpu_scheduled into > > arch_vcpu_is_preempted. We can then also get rid of the > > local cpu_is_preempted function by moving the > > CIF_ENABLED_WAIT test into arch_vcpu_is_preempted. > >=20 > > Signed-off-by: Christian Borntraeger > > --- >=20 > hi, Christian > thanks for your patch! >=20 > > arch/s390/include/asm/spinlock.h | 3 +++ > > arch/s390/kernel/smp.c | 9 +++++++-- > > arch/s390/lib/spinlock.c | 25 ++++++++----------------- > > 3 files changed, 18 insertions(+), 19 deletions(-) > >=20 > > diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/s= pinlock.h > > index 63ebf37..e16e02f 100644 > > --- a/arch/s390/include/asm/spinlock.h > > +++ b/arch/s390/include/asm/spinlock.h > > @@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned in= t old, unsigned int new) > > return __sync_bool_compare_and_swap(lock, old, new); > > } > >=20 > > +bool arch_vcpu_is_preempted(int cpu); > > +#define vcpu_is_preempted arch_vcpu_is_preempted > > + > > /* > > * Simple spin lock operations. There are two variants, one clears IR= Q's > > * on the local processor, one does not. > > diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c > > index 7b89a75..4aadd16 100644 > > --- a/arch/s390/kernel/smp.c > > +++ b/arch/s390/kernel/smp.c > > @@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address) > > return -1; > > } > >=20 > > -int smp_vcpu_scheduled(int cpu) > root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/ > arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu); > arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int c= pu) { return 1; } > arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu) > arch/s390/lib/spinlock.c:44: if (smp_vcpu_scheduled(cpu)) >=20 > > +bool arch_vcpu_is_preempted(int cpu) > > { > > - return pcpu_running(pcpu_devices + cpu); > > + if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu)) > > + return false; > > + if (pcpu_running(pcpu_devices + cpu)) > > + return false; > I saw smp_vcpu_scheduled() returns true always on !SMP system. >=20 > maybe we can do somegthing silimar. like below >=20 > #ifndef CONFIG_SMP > static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_fla= g_of(CIF_ENABLED_WAIT, cpu); } > #else > ... >=20 > but I can't help thinking that if this is a!SMP system, maybe we could on= ly > #ifndef CONFIG_SMP > static inline bool arch_vcpu_is_preempted(int cpu) { return false; } > #else Why do we need a vcpu_is_preempted() implementation for UP? Where will you use it? Regards, Boqun > ... >=20 >=20 > thanks > xinhui >=20 > > + return true; > > } > > +EXPORT_SYMBOL(arch_vcpu_is_preempted); > >=20 > > void smp_yield_cpu(int cpu) > > { > > diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c > > index e5f50a7..e48a48e 100644 > > --- a/arch/s390/lib/spinlock.c > > +++ b/arch/s390/lib/spinlock.c > > @@ -37,15 +37,6 @@ static inline void _raw_compare_and_delay(unsigned i= nt *lock, unsigned int old) > > asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock)); > > } > >=20 > > -static inline int cpu_is_preempted(int cpu) > > -{ > > - if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu)) > > - return 0; > > - if (smp_vcpu_scheduled(cpu)) > > - return 0; > > - return 1; > > -} > > - > > void arch_spin_lock_wait(arch_spinlock_t *lp) > > { > > unsigned int cpu =3D SPINLOCK_LOCKVAL; > > @@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) > > continue; > > } > > /* First iteration: check if the lock owner is running. */ > > - if (first_diag && cpu_is_preempted(~owner)) { > > + if (first_diag && arch_vcpu_is_preempted(~owner)) { > > smp_yield_cpu(~owner); > > first_diag =3D 0; > > continue; > > @@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) > > * yield the CPU unconditionally. For LPAR rely on the > > * sense running status. > > */ > > - if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) { > > + if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) { > > smp_yield_cpu(~owner); > > first_diag =3D 0; > > } > > @@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, = unsigned long flags) > > continue; > > } > > /* Check if the lock owner is running. */ > > - if (first_diag && cpu_is_preempted(~owner)) { > > + if (first_diag && arch_vcpu_is_preempted(~owner)) { > > smp_yield_cpu(~owner); > > first_diag =3D 0; > > continue; > > @@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp,= unsigned long flags) > > * yield the CPU unconditionally. For LPAR rely on the > > * sense running status. > > */ > > - if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) { > > + if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) { > > smp_yield_cpu(~owner); > > first_diag =3D 0; > > } > > @@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw) > > owner =3D 0; > > while (1) { > > if (count-- <=3D 0) { > > - if (owner && cpu_is_preempted(~owner)) > > + if (owner && arch_vcpu_is_preempted(~owner)) > > smp_yield_cpu(~owner); > > count =3D spin_retry; > > } > > @@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsign= ed int prev) > > owner =3D 0; > > while (1) { > > if (count-- <=3D 0) { > > - if (owner && cpu_is_preempted(~owner)) > > + if (owner && arch_vcpu_is_preempted(~owner)) > > smp_yield_cpu(~owner); > > count =3D spin_retry; > > } > > @@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw) > > owner =3D 0; > > while (1) { > > if (count-- <=3D 0) { > > - if (owner && cpu_is_preempted(~owner)) > > + if (owner && arch_vcpu_is_preempted(~owner)) > > smp_yield_cpu(~owner); > > count =3D spin_retry; > > } > > @@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu) > > { > > if (!cpu) > > return; > > - if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu)) > > + if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu)) > > return; > > smp_yield_cpu(~cpu); > > } > >=20 >=20 --ALfTUftag+2gvp1h Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEcBAABCAAGBQJX7f2pAAoJEEl56MO1B/q4SAYIAKDn78gdtlZJ7tjMjuu/hXSR kgVpphv7Kxz8PSEzG1j3oVebCpFF2LiqxhcTDA2P+7pXgR3OdAlAsmtCJ76y/epa nhRQaZZPByg3GO8ftt0EM2Q/kiMyGEI9JsT3dKMVfHbg2qxR9qiBW7QnNYbQihXq uZryO0jcHYY1zu7vISxbJrdJGHEOBGFlJR+70MwsX3QUzdrNK6XtkOpMOkfjAcaJ fljAH9GUyTpU01IILRiOX4cVn2PelhU84fDEu4hawly1U52b7/RSySpySTaKF5KC vDxEGe+aeCj4XS/Cz3fOFLoKrcVGknLxU73CH2vcPMHQS0ygN65Ke712nwi7N8g= =j4Ci -----END PGP SIGNATURE----- --ALfTUftag+2gvp1h--