Commit-ID: d9345c65eb7930ac6755cf593ee7686f4029ccf4 Gitweb: http://git.kernel.org/tip/d9345c65eb7930ac6755cf593ee7686f4029ccf4 Author: Pan Xinhui <xinhui....@linux.vnet.ibm.com> AuthorDate: Wed, 2 Nov 2016 05:08:28 -0400 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 22 Nov 2016 12:48:05 +0100
sched/core: Introduce the vcpu_is_preempted(cpu) interface This patch is the first step to add support to improve lock holder preemption beaviour. vcpu_is_preempted(cpu) does the obvious thing: it tells us whether a vCPU is preempted or not. Defaults to false on architectures that don't support it. Suggested-by: Peter Zijlstra (Intel) <pet...@infradead.org> Tested-by: Juergen Gross <jgr...@suse.com> Signed-off-by: Pan Xinhui <xinhui....@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> [ Translated the changelog to English. ] Acked-by: Christian Borntraeger <borntrae...@de.ibm.com> Acked-by: Paolo Bonzini <pbonz...@redhat.com> Cc: david.lai...@aculab.com Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: b...@kernel.crashing.org Cc: boqun.f...@gmail.com Cc: bsinghar...@gmail.com Cc: d...@stgolabs.net Cc: kernel...@gmail.com Cc: konrad.w...@oracle.com Cc: linuxppc-...@lists.ozlabs.org Cc: m...@ellerman.id.au Cc: paul...@linux.vnet.ibm.com Cc: pau...@samba.org Cc: rkrc...@redhat.com Cc: virtualizat...@lists.linux-foundation.org Cc: will.dea...@arm.com Cc: xen-devel-requ...@lists.xenproject.org Cc: xen-de...@lists.xenproject.org Link: http://lkml.kernel.org/r/1478077718-37424-2-git-send-email-xinhui....@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- include/linux/sched.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index dc37cbe..37261af 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -3510,6 +3510,18 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu) #endif /* CONFIG_SMP */ +/* + * In order to reduce various lock holder preemption latencies provide an + * interface to see if a vCPU is currently running or not. + * + * This allows us to terminate optimistic spin loops and block, analogous to + * the native optimistic spin heuristic of testing if the lock owner task is + * running or not. + */ +#ifndef vcpu_is_preempted +# define vcpu_is_preempted(cpu) false +#endif + extern long sched_setaffinity(pid_t pid, const struct cpumask *new_mask); extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
