From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH v3 0/4] implement vcpu preempted check Date: Thu, 29 Sep 2016 12:40:04 +0200 Message-ID: References: <1469101514-49475-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <20160929101040.GV5016@twins.programming.kicks-ass.net> <166f3bad-f700-4624-6c1c-996f90ad609c@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <166f3bad-f700-4624-6c1c-996f90ad609c@de.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Peter Zijlstra , Pan Xinhui Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, xen-devel-request@lists.xenproject.org, kvm@vger.kernel.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, Heiko Carstens List-ID: On 09/29/2016 12:23 PM, Christian Borntraeger wrote: > On 09/29/2016 12:10 PM, Peter Zijlstra wrote: >> On Thu, Jul 21, 2016 at 07:45:10AM -0400, Pan Xinhui wrote: >>> change from v2: >>> no code change, fix typos, update some comments >>> >>> change from v1: >>> a simplier definition of default vcpu_is_preempted >>> skip mahcine type check on ppc, and add config. remove dedicated macro. >>> add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner. >>> add more comments >>> thanks boqun and Peter's suggestion. >>> >>> This patch set aims to fix lock holder preemption issues. >> >> So I really like the concept, but I would also really like to see >> support for more hypervisors included before we can move forward with >> this. >> >> Please consider s390 and (x86/arm) KVM. Once we have a few, more can >> follow later, but I think its important to not only have PPC support for >> this. > > Actually the s390 preemted check via sigp sense running is available for > all hypervisors (z/VM, LPAR and KVM) which implies everywhere as you can no > longer buy s390 systems without LPAR. > > As Heiko already pointed out we could simply use a small inline function > that calls cpu_is_preempted from arch/s390/lib/spinlock (or smp_vcpu_scheduled from smp.c) Maybe something like (untested and just pasted, so white space damaged) diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h index 63ebf37..6e82986 100644 --- a/arch/s390/include/asm/spinlock.h +++ b/arch/s390/include/asm/spinlock.h @@ -21,6 +21,13 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new) return __sync_bool_compare_and_swap(lock, old, new); } +int arch_vcpu_is_preempted(int cpu); +#define vcpu_is_preempted cpu_is_preempted +static inline bool cpu_is_preempted(int cpu) +{ + return arch_vcpu_is_preempted(cpu); +} + /* * Simple spin lock operations. There are two variants, one clears IRQ's * on the local processor, one does not. diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c index e5f50a7..260d179 100644 --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -37,7 +37,7 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old) asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock)); } -static inline int cpu_is_preempted(int cpu) +int arch_vcpu_is_preempted(int cpu) { if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu)) return 0; @@ -45,6 +45,7 @@ static inline int cpu_is_preempted(int cpu) return 0; return 1; } +EXPORT_SYMBOL(arch_vcpu_is_preempted); void arch_spin_lock_wait(arch_spinlock_t *lp) { If ok I can respin into a proper patch.