]> git.ipfire.org Git - thirdparty/kernel/stable.git/commit
mm: slub: avoid wake up kswapd in set_track_prepare
authoryangshiguang <yangshiguang@xiaomi.com>
Sat, 30 Aug 2025 02:09:46 +0000 (10:09 +0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 9 Sep 2025 16:58:16 +0000 (18:58 +0200)
commit243b705a90ed8449f561a271cf251fd2e939f3db
tree7c287f2a2d8c6a59a0e7b551becfaf7739349a0d
parentcd0236550cf80d47c8beeb2917a6aa7cf6a77b9a
mm: slub: avoid wake up kswapd in set_track_prepare

commit 850470a8413a8a78e772c4f6bd9fe81ec6bd5b0f upstream.

set_track_prepare() can incur lock recursion.
The issue is that it is called from hrtimer_start_range_ns
holding the per_cpu(hrtimer_bases)[n].lock, but when enabled
CONFIG_DEBUG_OBJECTS_TIMERS, may wake up kswapd in set_track_prepare,
and try to hold the per_cpu(hrtimer_bases)[n].lock.

Avoid deadlock caused by implicitly waking up kswapd by passing in
allocation flags, which do not contain __GFP_KSWAPD_RECLAIM in the
debug_objects_fill_pool() case. Inside stack depot they are processed by
gfp_nested_mask().
Since ___slab_alloc() has preemption disabled, we mask out
__GFP_DIRECT_RECLAIM from the flags there.

The oops looks something like:

BUG: spinlock recursion on CPU#3, swapper/3/0
 lock: 0xffffff8a4bf29c80, .magic: dead4ead, .owner: swapper/3/0, .owner_cpu: 3
Hardware name: Qualcomm Technologies, Inc. Popsicle based on SM8850 (DT)
Call trace:
spin_bug+0x0
_raw_spin_lock_irqsave+0x80
hrtimer_try_to_cancel+0x94
task_contending+0x10c
enqueue_dl_entity+0x2a4
dl_server_start+0x74
enqueue_task_fair+0x568
enqueue_task+0xac
do_activate_task+0x14c
ttwu_do_activate+0xcc
try_to_wake_up+0x6c8
default_wake_function+0x20
autoremove_wake_function+0x1c
__wake_up+0xac
wakeup_kswapd+0x19c
wake_all_kswapds+0x78
__alloc_pages_slowpath+0x1ac
__alloc_pages_noprof+0x298
stack_depot_save_flags+0x6b0
stack_depot_save+0x14
set_track_prepare+0x5c
___slab_alloc+0xccc
__kmalloc_cache_noprof+0x470
__set_page_owner+0x2bc
post_alloc_hook[jt]+0x1b8
prep_new_page+0x28
get_page_from_freelist+0x1edc
__alloc_pages_noprof+0x13c
alloc_slab_page+0x244
allocate_slab+0x7c
___slab_alloc+0x8e8
kmem_cache_alloc_noprof+0x450
debug_objects_fill_pool+0x22c
debug_object_activate+0x40
enqueue_hrtimer[jt]+0xdc
hrtimer_start_range_ns+0x5f8
...

Signed-off-by: yangshiguang <yangshiguang@xiaomi.com>
Fixes: 5cf909c553e9 ("mm/slub: use stackdepot to save stack trace in objects")
Cc: stable@vger.kernel.org
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mm/slub.c