From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <waiman.long@hp.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
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: Re: [PATCH 8/9] qspinlock: Generic paravirt support
Date: Thu, 19 Mar 2015 14:43:36 +0100 [thread overview]
Message-ID: <20150319134336.GE11574@worktop.ger.corp.intel.com> (raw)
In-Reply-To: <20150319122536.GD11574@worktop.ger.corp.intel.com>
On Thu, Mar 19, 2015 at 01:25:36PM +0100, Peter Zijlstra wrote:
> +static struct qspinlock **pv_hash(struct qspinlock *lock)
> +{
> + u32 hash = hash_ptr(lock, PV_LOCK_HASH_BITS);
> + struct pv_hash_bucket *hb, *end;
> +
> + if (!hash)
> + hash = 1;
> +
> + hb = &__pv_lock_hash[hash_align(hash)];
> + for (;;) {
> + for (end = hb + PV_HB_PER_LINE; hb < end; hb++) {
> + if (cmpxchg(&hb->lock, NULL, HB_RESERVED)) {
That should be: !cmpxchg(), bit disturbing that that booted.
> + WRITE_ONCE(hb->cpu, smp_processor_id());
> + /*
> + * Since we must read lock first and cpu
> + * second, we must write cpu first and lock
> + * second, therefore use HB_RESERVE to mark an
> + * entry in use before writing the values.
> + *
> + * This can cause hb_hash_find() to not find a
> + * cpu even though _Q_SLOW_VAL, this is not a
> + * problem since we re-check l->locked before
> + * going to sleep and the unlock will have
> + * cleared l->locked already.
> + */
> + smp_wmb(); /* matches rmb from pv_hash_find */
> + WRITE_ONCE(hb->lock, lock);
> + goto done;
> + }
> + }
> +
> + hash = lfsr(hash, PV_LOCK_HASH_BITS);
> + hb = &__pv_lock_hash[hash_align(hash)];
> + }
> +
> +done:
> + return &hb->lock;
> +}
next prev parent reply other threads:[~2015-03-19 13:43 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 ` [PATCH 7/9] qspinlock: Revert to test-and-set on hypervisors Peter Zijlstra
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 [this message]
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
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