The patch titled
Subject: mm/hugetlb: fix possible recursive locking detected warning
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-fix-possible-recursive-locking-detected-warning.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-fix-possible-recursive-locking-detected-warning.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: mm/hugetlb: fix possible recursive locking detected warning
Date: Fri, 12 Jul 2024 11:13:14 +0800
When tries to demote 1G hugetlb folios, a lockdep warning is observed:
============================================
WARNING: possible recursive locking detected
6.10.0-rc6-00452-ga4d0275fa660-dirty #79 Not tainted
--------------------------------------------
bash/710 is trying to acquire lock:
ffffffff8f0a7850 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0x244/0x460
but task is already holding lock:
ffffffff8f0a6f48 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0xae/0x460
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&h->resize_lock);
lock(&h->resize_lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
4 locks held by bash/710:
#0: ffff8f118439c3f0 (sb_writers#5){.+.+}-{0:0}, at: ksys_write+0x64/0xe0
#1: ffff8f11893b9e88 (&of->mutex#2){+.+.}-{3:3}, at: kernfs_fop_write_iter+0xf8/0x1d0
#2: ffff8f1183dc4428 (kn->active#98){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x100/0x1d0
#3: ffffffff8f0a6f48 (&h->resize_lock){+.+.}-{3:3}, at: demote_store+0xae/0x460
stack backtrace:
CPU: 3 PID: 710 Comm: bash Not tainted 6.10.0-rc6-00452-ga4d0275fa660-dirty #79
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x68/0xa0
__lock_acquire+0x10f2/0x1ca0
lock_acquire+0xbe/0x2d0
__mutex_lock+0x6d/0x400
demote_store+0x244/0x460
kernfs_fop_write_iter+0x12c/0x1d0
vfs_write+0x380/0x540
ksys_write+0x64/0xe0
do_syscall_64+0xb9/0x1d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa61db14887
RSP: 002b:00007ffc56c48358 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fa61db14887
RDX: 0000000000000002 RSI: 000055a030050220 RDI: 0000000000000001
RBP: 000055a030050220 R08: 00007fa61dbd1460 R09: 000000007fffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007fa61dc1b780 R14: 00007fa61dc17600 R15: 00007fa61dc16a00
</TASK>
Lockdep considers this an AA deadlock because the different resize_lock
mutexes reside in the same lockdep class, but this is a false positive.
Place them in distinct classes to avoid these warnings.
Link: https://lkml.kernel.org/r/20240712031314.2570452-1-linmiaohe@xxxxxxxxxx
Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Acked-by: Muchun Song <muchun.song@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/hugetlb.h | 1 +
mm/hugetlb.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
--- a/include/linux/hugetlb.h~mm-hugetlb-fix-possible-recursive-locking-detected-warning
+++ a/include/linux/hugetlb.h
@@ -663,6 +663,7 @@ HPAGEFLAG(RawHwpUnreliable, raw_hwp_unre
/* Defines one hugetlb page size */
struct hstate {
struct mutex resize_lock;
+ struct lock_class_key resize_key;
int next_nid_to_alloc;
int next_nid_to_free;
unsigned int order;
--- a/mm/hugetlb.c~mm-hugetlb-fix-possible-recursive-locking-detected-warning
+++ a/mm/hugetlb.c
@@ -4645,7 +4645,7 @@ void __init hugetlb_add_hstate(unsigned
BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
BUG_ON(order < order_base_2(__NR_USED_SUBPAGE));
h = &hstates[hugetlb_max_hstate++];
- mutex_init(&h->resize_lock);
+ __mutex_init(&h->resize_lock, "resize mutex", &h->resize_key);
h->order = order;
h->mask = ~(huge_page_size(h) - 1);
for (i = 0; i < MAX_NUMNODES; ++i)
_
Patches currently in -mm which might be from linmiaohe@xxxxxxxxxx are
mm-memory-failure-remove-obsolete-mf_msg_different_compound.patch
mm-hugetlb-fix-potential-race-with-try_memory_failure_hugetlb.patch
mm-memory-failure-fix-vm_bug_on_pagepagepoisonedpage-when-unpoison-memory.patch
mm-hugetlb-fix-possible-recursive-locking-detected-warning.patch
