[+Cc: Thomas, Sebastian] Sorry, forgot to Cc you... :-/ On Tue, 7 Sept 2021 at 16:14, Marco Elver <elver@xxxxxxxxxx> wrote: > > Shuah Khan reported [1]: > > | When CONFIG_PROVE_RAW_LOCK_NESTING=y and CONFIG_KASAN are enabled, > | kasan_record_aux_stack() runs into "BUG: Invalid wait context" when > | it tries to allocate memory attempting to acquire spinlock in page > | allocation code while holding workqueue pool raw_spinlock. > | > | There are several instances of this problem when block layer tries > | to __queue_work(). Call trace from one of these instances is below: > | > | kblockd_mod_delayed_work_on() > | mod_delayed_work_on() > | __queue_delayed_work() > | __queue_work() (rcu_read_lock, raw_spin_lock pool->lock held) > | insert_work() > | kasan_record_aux_stack() > | kasan_save_stack() > | stack_depot_save() > | alloc_pages() > | __alloc_pages() > | get_page_from_freelist() > | rm_queue() > | rm_queue_pcplist() > | local_lock_irqsave(&pagesets.lock, flags); > | [ BUG: Invalid wait context triggered ] > > [1] https://lkml.kernel.org/r/20210902200134.25603-1-skhan@xxxxxxxxxxxxxxxxxxx > > PROVE_RAW_LOCK_NESTING is pointing out that (on RT kernels) the locking > rules are being violated. More generally, memory is being allocated from > a non-preemptive context (raw_spin_lock'd c-s) where it is not allowed. > > To properly fix this, we must prevent stackdepot from replenishing its > "stack slab" pool if memory allocations cannot be done in the current > context: it's a bug to use either GFP_ATOMIC nor GFP_NOWAIT in certain > non-preemptive contexts, including raw_spin_locks (see gfp.h and > ab00db216c9c7). > > The only downside is that saving a stack trace may fail if: stackdepot > runs out of space AND the same stack trace has not been recorded before. > I expect this to be unlikely, and a simple experiment (boot the kernel) > didn't result in any failure to record stack trace from insert_work(). > > The series includes a few minor fixes to stackdepot that I noticed in > preparing the series. It then introduces __stack_depot_save(), which > exposes the option to force stackdepot to not allocate any memory. > Finally, KASAN is changed to use the new stackdepot interface and > provide kasan_record_aux_stack_noalloc(), which is then used by > workqueue code. > > Marco Elver (6): > lib/stackdepot: include gfp.h > lib/stackdepot: remove unused function argument > lib/stackdepot: introduce __stack_depot_save() > kasan: common: provide can_alloc in kasan_save_stack() > kasan: generic: introduce kasan_record_aux_stack_noalloc() > workqueue, kasan: avoid alloc_pages() when recording stack > > include/linux/kasan.h | 2 ++ > include/linux/stackdepot.h | 6 +++++ > kernel/workqueue.c | 2 +- > lib/stackdepot.c | 51 ++++++++++++++++++++++++++++++-------- > mm/kasan/common.c | 6 ++--- > mm/kasan/generic.c | 14 +++++++++-- > mm/kasan/kasan.h | 2 +- > 7 files changed, 65 insertions(+), 18 deletions(-) > > -- > 2.33.0.153.gba50c8fa24-goog >
