linux-kernel - [PATCH 4/5] mm/hotplug: Avoid RCU stalls when removing large amounts of memory

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Date:   Mon, 17 Jun 2019 14:36:30 +1000
From:   "Alastair D'Silva" <alastair@....ibm.com>
To:     alastair@...ilva.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.com>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Juergen Gross <jgross@...e.com>, Qian Cai <cai@....pw>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jkosina@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Mukesh Ojha <mojha@...eaurora.org>,
        Arun KS <arunks@...eaurora.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] mm/hotplug: Avoid RCU stalls when removing large amounts of memory

From: Alastair D'Silva <alastair@...ilva.org>

When removing sufficiently large amounts of memory, we trigger RCU stall
detection. By periodically calling cond_resched(), we avoid bogus stall
warnings.

Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
---
 mm/memory_hotplug.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e096c987d261..382b3a0c9333 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -578,6 +578,9 @@ void __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 		__remove_section(zone, __pfn_to_section(pfn), map_offset,
 				 altmap);
 		map_offset = 0;
+
+		if (!(i & 0x0FFF))
+			cond_resched();
 	}
 
 	set_zone_contiguous(zone);
-- 
2.21.0