The patch titled
Subject: mm: might_sleep warning
has been added to the -mm tree. Its filename is
mm-initialize-pages-on-demand-during-boot-fix-4.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-initialize-pages-on-demand-during-boot-fix-4.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-initialize-pages-on-demand-during-boot-fix-4.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Subject: mm: might_sleep warning
Robot reported this issue:
https://lkml.org/lkml/2018/2/27/851
That is introduced by:
mm: initialize pages on demand during boot
The problem is caused by changing static branch value within spin lock.
Spin lock disables preemption, and changing static branch value takes
mutex lock in its path, and thus may sleep.
The fix is to add another boolean variable to avoid the need to change
static branch within spinlock.
Link: http://lkml.kernel.org/r/20180306192022.28289-1-pasha.tatashin@xxxxxxxxxx
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Steven Sistare <steven.sistare@xxxxxxxxxx>
Cc: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff -puN mm/page_alloc.c~mm-initialize-pages-on-demand-during-boot-fix-4 mm/page_alloc.c
--- a/mm/page_alloc.c~mm-initialize-pages-on-demand-during-boot-fix-4
+++ a/mm/page_alloc.c
@@ -1579,6 +1579,7 @@ static int __init deferred_init_memmap(v
* page_alloc_init_late() soon after smp_init() is complete.
*/
static __initdata DEFINE_SPINLOCK(deferred_zone_grow_lock);
+static bool deferred_zone_grow __initdata = true;
static DEFINE_STATIC_KEY_TRUE(deferred_pages);
/*
@@ -1616,7 +1617,7 @@ deferred_grow_zone(struct zone *zone, un
* Bail if we raced with another thread that disabled on demand
* initialization.
*/
- if (!static_branch_unlikely(&deferred_pages)) {
+ if (!static_branch_unlikely(&deferred_pages) || !deferred_zone_grow) {
spin_unlock_irqrestore(&deferred_zone_grow_lock, flags);
return false;
}
@@ -1683,10 +1684,15 @@ void __init page_alloc_init_late(void)
/*
* We are about to initialize the rest of deferred pages, permanently
* disable on-demand struct page initialization.
+ *
+ * Note: it is prohibited to modify static branches in non-preemptible
+ * context. Since, spin_lock() disables preemption, we must use an
+ * extra boolean deferred_zone_grow.
*/
spin_lock(&deferred_zone_grow_lock);
- static_branch_disable(&deferred_pages);
+ deferred_zone_grow = false;
spin_unlock(&deferred_zone_grow_lock);
+ static_branch_disable(&deferred_pages);
/* There will be num_node_state(N_MEMORY) threads */
atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY));
_
Patches currently in -mm which might be from pasha.tatashin@xxxxxxxxxx are
mm-initialize-pages-on-demand-during-boot.patch
mm-initialize-pages-on-demand-during-boot-fix-3.patch
mm-initialize-pages-on-demand-during-boot-fix-4.patch
mm-memory_hotplug-enforce-block-size-aligned-range-check.patch
x86-mm-memory_hotplug-determine-block-size-based-on-the-end-of-boot-memory.patch
x86-mm-memory_hotplug-determine-block-size-based-on-the-end-of-boot-memory-v4.patch
mm-uninitialized-struct-page-poisoning-sanity-checking.patch
mm-uninitialized-struct-page-poisoning-sanity-checking-v4.patch
mm-memory_hotplug-optimize-probe-routine.patch
mm-memory_hotplug-dont-read-nid-from-struct-page-during-hotplug.patch
mm-memory_hotplug-dont-read-nid-from-struct-page-during-hotplug-v5.patch
mm-memory_hotplug-optimize-memory-hotplug.patch
mm-memory_hotplug-optimize-memory-hotplug-v5.patch
xen-mm-allow-deferred-page-initialization-for-xen-pv-domains.patch
sparc64-ng4-memset-32-bits-overflow.patch
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