Linux-rt-users Archive on lore.kernel.org
 help / color / Atom feed
From: Mel Gorman <mgorman@techsingularity.net>
To: Linux-MM <linux-mm@kvack.org>,
	Linux-RT-Users <linux-rt-users@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Chuck Lever <chuck.lever@oracle.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Michal Hocko <mhocko@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 07/10] mm/page_alloc: Explicitly acquire the zone lock in __free_pages_ok
Date: Mon, 19 Apr 2021 15:13:38 +0100
Message-ID: <20210419141341.26047-8-mgorman@techsingularity.net> (raw)
In-Reply-To: <20210419141341.26047-1-mgorman@techsingularity.net>

__free_pages_ok() disables IRQs before calling a common helper
free_one_page() that acquires the zone lock. This is not safe according
to Documentation/locking/locktypes.rst and in this context, IRQ disabling
is not protecting a per_cpu_pages structure either or a local_lock would
be used.

This patch explicitly acquires the lock with spin_lock_irqsave instead of
relying on a helper. This removes the last instance of local_irq_save()
in page_alloc.c.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/page_alloc.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 295624fe293b..c6e8da942905 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1547,21 +1547,21 @@ static void __free_pages_ok(struct page *page, unsigned int order,
 	unsigned long flags;
 	int migratetype;
 	unsigned long pfn = page_to_pfn(page);
+	struct zone *zone = page_zone(page);
 
 	if (!free_pages_prepare(page, order, true))
 		return;
 
 	migratetype = get_pfnblock_migratetype(page, pfn);
 
-	/*
-	 * TODO FIX: Disable IRQs before acquiring IRQ-safe zone->lock
-	 * and protect vmstat updates.
-	 */
-	local_irq_save(flags);
+	spin_lock_irqsave(&zone->lock, flags);
 	__count_vm_events(PGFREE, 1 << order);
-	free_one_page(page_zone(page), page, pfn, order, migratetype,
-		      fpi_flags);
-	local_irq_restore(flags);
+	if (unlikely(has_isolate_pageblock(zone) ||
+		is_migrate_isolate(migratetype))) {
+		migratetype = get_pfnblock_migratetype(page, pfn);
+	}
+	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
+	spin_unlock_irqrestore(&zone->lock, flags);
 }
 
 void __free_pages_core(struct page *page, unsigned int order)
-- 
2.26.2


  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-19 14:13 [PATCH 00/10 v4] Use local_lock for pcp protection and reduce stat overhead Mel Gorman
2021-04-19 14:13 ` [PATCH 01/10] mm/page_alloc: Split per cpu page lists and zone stats Mel Gorman
2021-04-19 14:13 ` [PATCH 02/10] mm/page_alloc: Convert per-cpu list protection to local_lock Mel Gorman
2021-04-19 14:13 ` [PATCH 03/10] mm/vmstat: Convert NUMA statistics to basic NUMA counters Mel Gorman
2021-04-19 14:13 ` [PATCH 04/10] mm/vmstat: Inline NUMA event counter updates Mel Gorman
2021-04-19 14:13 ` [PATCH 05/10] mm/page_alloc: Batch the accounting updates in the bulk allocator Mel Gorman
2021-04-19 14:13 ` [PATCH 06/10] mm/page_alloc: Reduce duration that IRQs are disabled for VM counters Mel Gorman
2021-04-19 14:13 ` Mel Gorman [this message]
2021-04-19 14:13 ` [PATCH 08/10] mm/page_alloc: Avoid conflating IRQs disabled with zone->lock Mel Gorman
2021-04-19 14:13 ` [PATCH 09/10] mm/page_alloc: Update PGFREE outside the zone lock in __free_pages_ok Mel Gorman
2021-04-19 14:13 ` [PATCH 10/10] mm/page_alloc: Embed per_cpu_pages locking within the per-cpu structure Mel Gorman

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=20210419141341.26047-8-mgorman@techsingularity.net \
    --to=mgorman@techsingularity.net \
    --cc=brouer@redhat.com \
    --cc=chuck.lever@oracle.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-rt-users@vger.kernel.org \
    --cc=mhocko@kernel.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=vbabka@suse.cz \
    /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

Linux-rt-users Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-rt-users/0 linux-rt-users/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-rt-users linux-rt-users/ https://lore.kernel.org/linux-rt-users \
		linux-rt-users@vger.kernel.org
	public-inbox-index linux-rt-users

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-rt-users


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git