From: Qian Cai <cai@lca.pw>
To: akpm@linux-foundation.org
Cc: mhocko@kernel.org, sergey.senozhatsky.work@gmail.com,
pmladek@suse.com, rostedt@goodmis.org, peterz@infradead.org,
david@redhat.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH -next] mm/hotplug: silence a lockdep splat with printk()
Date: Tue, 14 Jan 2020 15:11:14 -0500 [thread overview]
Message-ID: <20200114201114.14696-1-cai@lca.pw> (raw)
Similar to the recent commit [1] merged into the random and -next trees,
it is not a good idea to call printk() with zone->lock held. The
standard fix is to use printk_deferred() in those places, but memory
offline will call dump_page() which need to defer after the lock. While
at it, remove a similar but unnecessary debug printk() as well.
[1] https://lore.kernel.org/lkml/1573679785-21068-1-git-send-email-cai@lca.pw/
Signed-off-by: Qian Cai <cai@lca.pw>
---
include/linux/page-isolation.h | 2 +-
mm/memory_hotplug.c | 2 +-
mm/page_alloc.c | 12 +++++-------
mm/page_isolation.c | 10 +++++++++-
4 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 148e65a9c606..5d8ba078006f 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -34,7 +34,7 @@ static inline bool is_migrate_isolate(int migratetype)
#define REPORT_FAILURE 0x2
bool has_unmovable_pages(struct zone *zone, struct page *page, int migratetype,
- int flags);
+ int flags, char *dump);
void set_pageblock_migratetype(struct page *page, int migratetype);
int move_freepages_block(struct zone *zone, struct page *page,
int migratetype, int *num_movable);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 7a6de9b0dcab..f10928538fa3 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1149,7 +1149,7 @@ static bool is_pageblock_removable_nolock(unsigned long pfn)
return false;
return !has_unmovable_pages(zone, page, MIGRATE_MOVABLE,
- MEMORY_OFFLINE);
+ MEMORY_OFFLINE, NULL);
}
/* Checks if this range of memory is likely to be hot-removable. */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e56cd1f33242..b6bec3925e80 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8204,7 +8204,7 @@ void *__init alloc_large_system_hash(const char *tablename,
* race condition. So you can't expect this function should be exact.
*/
bool has_unmovable_pages(struct zone *zone, struct page *page, int migratetype,
- int flags)
+ int flags, char *dump)
{
unsigned long iter = 0;
unsigned long pfn = page_to_pfn(page);
@@ -8305,8 +8305,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int migratetype,
return false;
unmovable:
WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
- if (flags & REPORT_FAILURE)
- dump_page(pfn_to_page(pfn + iter), reason);
+ if (flags & REPORT_FAILURE) {
+ page = pfn_to_page(pfn + iter);
+ strscpy(dump, reason, 64);
+ }
return true;
}
@@ -8711,10 +8713,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
BUG_ON(!PageBuddy(page));
order = page_order(page);
offlined_pages += 1 << order;
-#ifdef CONFIG_DEBUG_VM
- pr_info("remove from free list %lx %d %lx\n",
- pfn, 1 << order, end_pfn);
-#endif
del_page_from_free_area(page, &zone->free_area[order]);
pfn += (1 << order);
}
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 1f8b9dfecbe8..ce0fe3c1ceff 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -20,6 +20,7 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
struct zone *zone;
unsigned long flags;
int ret = -EBUSY;
+ char dump[64];
zone = page_zone(page);
@@ -37,7 +38,8 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
* FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
* We just check MOVABLE pages.
*/
- if (!has_unmovable_pages(zone, page, migratetype, isol_flags)) {
+ if (!has_unmovable_pages(zone, page, migratetype, isol_flags,
+ dump)) {
unsigned long nr_pages;
int mt = get_pageblock_migratetype(page);
@@ -54,6 +56,12 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
spin_unlock_irqrestore(&zone->lock, flags);
if (!ret)
drain_all_pages(zone);
+ else if (isol_flags & REPORT_FAILURE)
+ /*
+ * printk() with zone->lock held will guarantee to trigger a
+ * lockdep splat, so defer it here.
+ */
+ dump_page(page, dump);
return ret;
}
--
2.21.0 (Apple Git-122.2)
next reply other threads:[~2020-01-14 20:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-14 20:11 Qian Cai [this message]
2020-01-14 20:20 ` [PATCH -next] mm/hotplug: silence a lockdep splat with printk() David Hildenbrand
2020-01-14 21:02 ` Michal Hocko
2020-01-14 21:40 ` Qian Cai
2020-01-14 23:53 ` Andrew Morton
2020-01-15 1:02 ` Qian Cai
2020-01-15 1:19 ` Andrew Morton
2020-01-15 1:38 ` Qian Cai
2020-01-15 8:37 ` Michal Hocko
2020-01-15 9:52 ` Petr Mladek
[not found] ` <D6F57A74-7608-43BE-B909-4350DE95B68C@lca.pw>
2020-01-15 17:02 ` Petr Mladek
2020-01-15 17:16 ` Qian Cai
2020-01-16 14:29 ` Petr Mladek
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