| Message ID | 20220420122817.67181-1-caoyixuan2019@email.szu.edu.cn (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/page_owner.c: use get_task_comm() to record task command name with the protection of task_lock() | expand |
On Wed, Apr 20, 2022 at 08:28:17PM +0800, Yixuan Cao wrote: > I noticed that it is advised to access task command name with > [gs]et_task_comm() in the comment of task_struct->comm, > which is safer with the protection of task_lock(). > > Relative comment in include/linux/sched.h is as follows: > > /* > * executable name, excluding path. > * > * - normally initialized setup_new_exec() > * - access it with [gs]et_task_comm() > * - lock it with task_lock() > */ > > Signed-off-by: Yixuan Cao <caoyixuan2019@email.szu.edu.cn> > --- > mm/page_owner.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 2743062e92c2..bda8fe2660c0 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -171,8 +171,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext, > page_owner->pid = current->pid; > page_owner->tgid = current->tgid; > page_owner->ts_nsec = local_clock(); > - strlcpy(page_owner->comm, current->comm, > - sizeof(page_owner->comm)); > + get_task_comm(page_owner->comm, current); We can't call that thing here. WARNING: inconsistent lock state 5.18.0-rc3-next-20220421-dirty #22 Not tainted -------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. swapper/4/0 [HC0[0]:SC1[1]:HE1:SE0] takes: ffff07ff89ad87f8 (&p->alloc_lock){+.?.}-{2:2}, at: __get_task_comm {SOFTIRQ-ON-W} state was registered at: __lock_acquire lock_acquire.part.0 lock_acquire _raw_spin_lock __set_task_comm kthreadd ret_from_fork irq event stamp: 50532 hardirqs last enabled at (50532): seqcount_lockdep_reader_access hardirqs last disabled at (50531): seqcount_lockdep_reader_access softirqs last enabled at (50306): __do_softirq softirqs last disabled at (50313): __irq_exit_rcu other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&p->alloc_lock); <Interrupt> lock(&p->alloc_lock); *** DEADLOCK *** 1 lock held by swapper/4/0: #0: ffffce91c3d81da0 (rcu_callback){....}-{0:0}, at: rcu_do_batch stack backtrace: CPU: 4 PID: 0 Comm: swapper/4 Not tainted 5.18.0-rc3-next-20220421-dirty #22 Call trace: dump_backtrace show_stack dump_stack_lvl dump_stack print_usage_bug.part.0 mark_lock_irq mark_lock mark_usage __lock_acquire lock_acquire.part.0 lock_acquire _raw_spin_lock __get_task_comm __get_task_comm at fs/exec.c:1221 __set_page_owner arch___set_bit at include/asm-generic/bitops/non-atomic.h:22 (inlined by) __set_page_owner_handle at mm/page_owner.c:175 (inlined by) __set_page_owner at mm/page_owner.c:192 post_alloc_hook get_page_from_freelist __alloc_pages alloc_pages allocate_slab new_slab ___slab_alloc __slab_alloc.constprop.0 kmem_cache_alloc fill_pool __debug_object_init debug_object_activate call_rcu put_object __delete_object kmemleak_free slab_free_freelist_hook kmem_cache_free file_free_rcu rcu_do_batch rcu_core rcu_core_si __do_softirq __irq_exit_rcu irq_exit_rcu el1_interrupt el1h_64_irq_handler el1h_64_irq arch_local_irq_enable default_idle_call cpuidle_idle_call do_idle cpu_startup_entry secondary_start_kernel __secondary_switched
diff --git a/mm/page_owner.c b/mm/page_owner.c index 2743062e92c2..bda8fe2660c0 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -171,8 +171,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext, page_owner->pid = current->pid; page_owner->tgid = current->tgid; page_owner->ts_nsec = local_clock(); - strlcpy(page_owner->comm, current->comm, - sizeof(page_owner->comm)); + get_task_comm(page_owner->comm, current); __set_bit(PAGE_EXT_OWNER, &page_ext->flags); __set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
I noticed that it is advised to access task command name with [gs]et_task_comm() in the comment of task_struct->comm, which is safer with the protection of task_lock(). Relative comment in include/linux/sched.h is as follows: /* * executable name, excluding path. * * - normally initialized setup_new_exec() * - access it with [gs]et_task_comm() * - lock it with task_lock() */ Signed-off-by: Yixuan Cao <caoyixuan2019@email.szu.edu.cn> --- mm/page_owner.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)