LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman.Long@hp.com
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	peterz@infradead.org, paolo.bonzini@gmail.com,
	konrad.wilk@oracle.com, boris.ostrovsky@oracle.com,
	paulmck@linux.vnet.ibm.com, riel@redhat.com,
	torvalds@linux-foundation.org, raghavendra.kt@linux.vnet.ibm.com,
	david.vrabel@citrix.com, oleg@redhat.com, scott.norton@hp.com,
	doug.hatch@hp.com, linux-arch@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	xen-devel@lists.xenproject.org, kvm@vger.kernel.org,
	luto@amacapital.net
Subject: [PATCH 7/9] qspinlock: Revert to test-and-set on hypervisors
Date: Mon, 16 Mar 2015 14:16:20 +0100	[thread overview]
Message-ID: <20150316133112.211733056@infradead.org> (raw)
In-Reply-To: <20150316131613.720617163@infradead.org>

[-- Attachment #1: peter_zijlstra-qspinlock-revert_to_test-and-set_on_hypervisors.patch --]
[-- Type: text/plain, Size: 2555 bytes --]

From: Peter Zijlstra <peterz@infradead.org>

When we detect a hypervisor (!paravirt, see qspinlock paravirt support
patches), revert to a simple test-and-set lock to avoid the horrors
of queue preemption.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1421784755-21945-8-git-send-email-Waiman.Long@hp.com
---
 arch/x86/include/asm/qspinlock.h |   14 ++++++++++++++
 include/asm-generic/qspinlock.h  |    7 +++++++
 kernel/locking/qspinlock.c       |    3 +++
 3 files changed, 24 insertions(+)

--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -1,6 +1,7 @@
 #ifndef _ASM_X86_QSPINLOCK_H
 #define _ASM_X86_QSPINLOCK_H
 
+#include <asm/cpufeature.h>
 #include <asm-generic/qspinlock_types.h>
 
 #define	queue_spin_unlock queue_spin_unlock
@@ -15,6 +16,19 @@ static inline void queue_spin_unlock(str
 	smp_store_release((u8 *)lock, 0);
 }
 
+#define virt_queue_spin_lock virt_queue_spin_lock
+
+static inline bool virt_queue_spin_lock(struct qspinlock *lock)
+{
+	if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
+		return false;
+
+	while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0)
+		cpu_relax();
+
+	return true;
+}
+
 #include <asm-generic/qspinlock.h>
 
 #endif /* _ASM_X86_QSPINLOCK_H */
--- a/include/asm-generic/qspinlock.h
+++ b/include/asm-generic/qspinlock.h
@@ -111,6 +111,13 @@ static inline void queue_spin_unlock_wai
 		cpu_relax();
 }
 
+#ifndef virt_queue_spin_lock
+static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock)
+{
+	return false;
+}
+#endif
+
 /*
  * Initializier
  */
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -259,6 +259,9 @@ void queue_spin_lock_slowpath(struct qsp
 
 	BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS));
 
+	if (virt_queue_spin_lock(lock))
+		return;
+
 	/*
 	 * wait for in-progress pending->locked hand-overs
 	 *



  parent reply	other threads:[~2015-03-16 13:38 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-16 13:16 [PATCH 0/9] qspinlock stuff -v15 Peter Zijlstra
2015-03-16 13:16 ` [PATCH 1/9] qspinlock: A simple generic 4-byte queue spinlock Peter Zijlstra
2015-03-16 13:16 ` [PATCH 2/9] qspinlock, x86: Enable x86-64 to use " Peter Zijlstra
2015-03-16 13:16 ` [PATCH 3/9] qspinlock: Add pending bit Peter Zijlstra
2015-03-16 13:16 ` [PATCH 4/9] qspinlock: Extract out code snippets for the next patch Peter Zijlstra
2015-03-16 13:16 ` [PATCH 5/9] qspinlock: Optimize for smaller NR_CPUS Peter Zijlstra
2015-03-16 13:16 ` [PATCH 6/9] qspinlock: Use a simple write to grab the lock Peter Zijlstra
2015-03-16 13:16 ` Peter Zijlstra [this message]
2015-03-16 13:16 ` [PATCH 8/9] qspinlock: Generic paravirt support Peter Zijlstra
     [not found]   ` <5509E51D.7040909@hp.com>
2015-03-19 10:12     ` Peter Zijlstra
2015-03-19 12:25       ` Peter Zijlstra
2015-03-19 13:43         ` Peter Zijlstra
2015-03-19 23:25         ` Waiman Long
2015-04-01 16:20         ` Waiman Long
2015-04-01 17:12           ` Peter Zijlstra
2015-04-01 17:42             ` Peter Zijlstra
2015-04-01 18:17               ` Peter Zijlstra
2015-04-01 18:54                 ` Waiman Long
2015-04-01 18:48                   ` Peter Zijlstra
2015-04-01 19:58                     ` Waiman Long
2015-04-01 21:03                       ` Peter Zijlstra
2015-04-02 16:28                         ` Waiman Long
2015-04-02 17:20                           ` Peter Zijlstra
2015-04-02 19:48                             ` Peter Zijlstra
2015-04-03  3:39                               ` Waiman Long
2015-04-03 13:43                               ` Peter Zijlstra
2015-04-01 20:10             ` Waiman Long
2015-03-16 13:16 ` [PATCH 9/9] qspinlock,x86,kvm: Implement KVM support for paravirt qspinlock Peter Zijlstra
     [not found]   ` <550A3863.2060808@hp.com>
2015-03-19 10:01     ` Peter Zijlstra
2015-03-19 21:08       ` Waiman Long
2015-03-20  7:43         ` Raghavendra K T
2015-03-16 14:08 ` [Xen-devel] [PATCH 0/9] qspinlock stuff -v15 David Vrabel
2015-03-18 20:36 ` Waiman Long
2015-03-19 18:01 ` [Xen-devel] " David Vrabel
2015-03-19 18:32   ` Peter Zijlstra
2015-03-25 19:47 ` Konrad Rzeszutek Wilk
2015-03-26 20:21   ` Peter Zijlstra
2015-03-27 14:07     ` Konrad Rzeszutek Wilk
2015-03-30 16:41       ` Waiman Long
2015-03-30 16:25   ` Waiman Long
2015-03-30 16:29     ` Peter Zijlstra
2015-03-30 16:43       ` Waiman Long
2015-03-27  6:40 ` Raghavendra K T

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20150316133112.211733056@infradead.org \
    --to=peterz@infradead.org \
    --cc=Waiman.Long@hp.com \
    --cc=boris.ostrovsky@oracle.com \
    --cc=david.vrabel@citrix.com \
    --cc=doug.hatch@hp.com \
    --cc=hpa@zytor.com \
    --cc=konrad.wilk@oracle.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@amacapital.net \
    --cc=mingo@redhat.com \
    --cc=oleg@redhat.com \
    --cc=paolo.bonzini@gmail.com \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=raghavendra.kt@linux.vnet.ibm.com \
    --cc=riel@redhat.com \
    --cc=scott.norton@hp.com \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=virtualization@lists.linux-foundation.org \
    --cc=x86@kernel.org \
    --cc=xen-devel@lists.xenproject.org \
    --subject='Re: [PATCH 7/9] qspinlock: Revert to test-and-set on hypervisors' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).