Re: [PATCH v3 02/14] mm/mmu_notifier: add an interval tree notifier

From: Jason Gunthorpe <jgg@mellanox.com>
To: Ralph Campbell <rcampbell@nvidia.com>
Cc: "nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	David Zhou <David1.Zhou@amd.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
	Christoph Hellwig <hch@infradead.org>,
	Ben Skeggs <bskeggs@redhat.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Philip Yang <Philip.Yang@amd.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Jerome Glisse <jglisse@redhat.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Petr Cvek <petrcvekcz@gmail.com>, Juergen Gross <jgross@suse.com>,
	Mike Marciniszyn <mike.marciniszyn@intel.com>,
	"Felix.Kuehling@amd.com" <Felix.Kuehl>
Subject: Re: [PATCH v3 02/14] mm/mmu_notifier: add an interval tree notifier
Date: Sat, 23 Nov 2019 23:59:53 +0000	[thread overview]
Message-ID: <20191123235949.GE7481@mellanox.com> (raw)
In-Reply-To: <cc5d4d76-df30-af7f-931c-eed8a7ada122@nvidia.com>

On Fri, Nov 22, 2019 at 04:54:08PM -0800, Ralph Campbell wrote:

> Actually, I think you can remove the "need_wake" variable since it is
> unconditionally set to "true".

Oh, yes, thank you. An earlier revision had a different control flow
 
> Also, the comment in__mmu_interval_notifier_insert() says
> "mni->mr_invalidate_seq" and I think that should be
> "mni->invalidate_seq".

Got it.

I squashed this in:

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index b3a064b3b31807..30abbfdc25be55 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -129,7 +129,6 @@ static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
 {
 	struct mmu_interval_notifier *mni;
 	struct hlist_node *next;
-	bool need_wake = false;
 
 	spin_lock(&mmn_mm->lock);
 	if (--mmn_mm->active_invalidate_ranges ||
@@ -140,7 +139,6 @@ static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
 
 	/* Make invalidate_seq even */
 	mmn_mm->invalidate_seq++;
-	need_wake = true;
 
 	/*
 	 * The inv_end incorporates a deferred mechanism like rtnl_unlock().
@@ -160,8 +158,7 @@ static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
 	}
 	spin_unlock(&mmn_mm->lock);
 
-	if (need_wake)
-		wake_up_all(&mmn_mm->wq);
+	wake_up_all(&mmn_mm->wq);
 }
 
 /**
@@ -884,7 +881,7 @@ static int __mmu_interval_notifier_insert(
 	 * possibility for live lock, instead defer the add to
 	 * mn_itree_inv_end() so this algorithm is deterministic.
 	 *
-	 * In all cases the value for the mni->mr_invalidate_seq should be
+	 * In all cases the value for the mni->invalidate_seq should be
 	 * odd, see mmu_interval_read_begin()
 	 */
 	spin_lock(&mmn_mm->lock);

Jason

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