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McKenney" To: Uladzislau Rezki Cc: Jun Miao , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , Dmitry Vyukov , qiang.zhang1211@gmail.com, RCU , LKML , miaojun0823@163.com, ryabinin.a.a@gmail.com, Alexander Potapenko , jianwei.hu@windriver.com, melver@google.com Subject: Re: [PATCH] rcu: avoid alloc_pages() when recording stack Message-ID: <20211103181315.GT880162@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20211101103158.3725704-1-jun.miao@windriver.com> <96f9d669-b9da-f387-199e-e6bf36081fbd@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 03, 2021 at 02:55:48PM +0100, Uladzislau Rezki wrote: > On Wed, Nov 3, 2021 at 7:51 AM Jun Miao wrote: > > > > > > On 11/2/21 10:53 PM, Uladzislau Rezki wrote: > > > [Please note: This e-mail is from an EXTERNAL e-mail address] > > > > > >> Add KASAN maintainers > > >> > > >> On 11/1/21 6:31 PM, Jun Miao wrote: > > >>> The default kasan_record_aux_stack() calls stack_depot_save() with GFP_NOWAIT, > > >>> which in turn can then call alloc_pages(GFP_NOWAIT, ...). In general, however, > > >>> it is not even possible to use either GFP_ATOMIC nor GFP_NOWAIT in certain > > >>> non-preemptive contexts/RT kernel including raw_spin_locks (see gfp.h and ab00db216c9c7). > > >>> > > >>> Fix it by instructing stackdepot to not expand stack storage via alloc_pages() > > >>> in case it runs out by using kasan_record_aux_stack_noalloc(). > > >>> > > >>> Jianwei Hu reported: > > >>> BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:969 > > >>> in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 15319, name: python3 > > >>> INFO: lockdep is turned off. > > >>> irq event stamp: 0 > > >>> hardirqs last enabled at (0): [<0000000000000000>] 0x0 > > >>> hardirqs last disabled at (0): [] copy_process+0xaf3/0x2590 > > >>> softirqs last enabled at (0): [] copy_process+0xaf3/0x2590 > > >>> softirqs last disabled at (0): [<0000000000000000>] 0x0 > > >>> CPU: 6 PID: 15319 Comm: python3 Tainted: G W O 5.15-rc7-preempt-rt #1 > > >>> Hardware name: Supermicro SYS-E300-9A-8C/A2SDi-8C-HLN4F, BIOS 1.1b 12/17/2018 > > >>> Call Trace: > > >>> show_stack+0x52/0x58 > > >>> dump_stack+0xa1/0xd6 > > >>> ___might_sleep.cold+0x11c/0x12d > > >>> rt_spin_lock+0x3f/0xc0 > > >>> rmqueue+0x100/0x1460 > > >>> rmqueue+0x100/0x1460 > > >>> mark_usage+0x1a0/0x1a0 > > >>> ftrace_graph_ret_addr+0x2a/0xb0 > > >>> rmqueue_pcplist.constprop.0+0x6a0/0x6a0 > > >>> __kasan_check_read+0x11/0x20 > > >>> __zone_watermark_ok+0x114/0x270 > > >>> get_page_from_freelist+0x148/0x630 > > >>> is_module_text_address+0x32/0xa0 > > >>> __alloc_pages_nodemask+0x2f6/0x790 > > >>> __alloc_pages_slowpath.constprop.0+0x12d0/0x12d0 > > >>> create_prof_cpu_mask+0x30/0x30 > > >>> alloc_pages_current+0xb1/0x150 > > >>> stack_depot_save+0x39f/0x490 > > >>> kasan_save_stack+0x42/0x50 > > >>> kasan_save_stack+0x23/0x50 > > >>> kasan_record_aux_stack+0xa9/0xc0 > > >>> __call_rcu+0xff/0x9c0 > > >>> call_rcu+0xe/0x10 > > >>> put_object+0x53/0x70 > > >>> __delete_object+0x7b/0x90 > > >>> kmemleak_free+0x46/0x70 > > >>> slab_free_freelist_hook+0xb4/0x160 > > >>> kfree+0xe5/0x420 > > >>> kfree_const+0x17/0x30 > > >>> kobject_cleanup+0xaa/0x230 > > >>> kobject_put+0x76/0x90 > > >>> netdev_queue_update_kobjects+0x17d/0x1f0 > > >>> ... ... > > >>> ksys_write+0xd9/0x180 > > >>> __x64_sys_write+0x42/0x50 > > >>> do_syscall_64+0x38/0x50 > > >>> entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > >>> > > >>> Fixes: 84109ab58590 ("rcu: Record kvfree_call_rcu() call stack for KASAN") > > >>> Fixes: 26e760c9a7c8 ("rcu: kasan: record and print call_rcu() call stack") > > >>> Reported-by: Jianwei Hu > > >>> Signed-off-by: Jun Miao > > >>> --- > > >>> kernel/rcu/tree.c | 4 ++-- > > >>> 1 file changed, 2 insertions(+), 2 deletions(-) > > >>> > > >>> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > >>> index 8270e58cd0f3..2c1034580f15 100644 > > >>> --- a/kernel/rcu/tree.c > > >>> +++ b/kernel/rcu/tree.c > > >>> @@ -3026,7 +3026,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) > > >>> head->func = func; > > >>> head->next = NULL; > > >>> local_irq_save(flags); > > >>> - kasan_record_aux_stack(head); > > >>> + kasan_record_aux_stack_noalloc(head); > > >>> rdp = this_cpu_ptr(&rcu_data); > > >>> > > >>> /* Add the callback to our list. */ > > >>> @@ -3591,7 +3591,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > >>> return; > > >>> } > > >>> > > >>> - kasan_record_aux_stack(ptr); > > >>> + kasan_record_aux_stack_noalloc(ptr); > > >>> success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head); > > >>> if (!success) { > > >>> run_page_cache_worker(krcp); > > > Yep an allocation is tricky here. This change looks correct to me at > > > least from the point that it does not allocate. > > > > > > -- > > > Uladzislau Rezki > > > > Thanks your approval. Could you like to give me a review? > > > Reviewed-by: Uladzislau Rezki (Sony) I have queued it for review and testing, thank you both! I do have some remaining concerns about this code being starved for memory. I am wondering if the code needs to check the interrupt state. And perhaps also whether locks are held. I of course will refrain from sending this to mainline until these concerns are resolved. Marco, Dmitry, thoughts? Thanx, Paul