On Wed, Mar 02, 2022 at 04:36:38AM +0000, Hyeonggon Yoo wrote: > On Mon, Feb 28, 2022 at 06:56:39PM +0900, Byungchul Park wrote: > > I didn't want to bother you so I was planning to send the next spin > > after making more progress. However, PATCH v2 reports too many false > > positives because Dept tracked the bit_wait_table[] wrong way - I > > apologize for that. So I decided to send PATCH v3 first before going > > further for those who want to run Dept for now. > > > > There might still be some false positives but not overwhelming. > > > > Hello Byungchul, I'm running DEPT v3 on my system > and I see report below. > > Looking at the kmemleak code and comment, I think > kmemleak tried to avoid lockdep recursive warning > but detected by DEPT? > > =================================================== > DEPT: Circular dependency has been detected. > 5.17.0-rc1+ #1 Tainted: G W > --------------------------------------------------- > summary > --------------------------------------------------- > *** AA DEADLOCK *** > > context A > [S] __raw_spin_lock_irqsave(&object->lock:0) > [W] _raw_spin_lock_nested(&object->lock:0) > [E] spin_unlock(&object->lock:0) > > [S]: start of the event context > [W]: the wait blocked > [E]: the event not reachable > --------------------------------------------------- > context A's detail > --------------------------------------------------- > context A > [S] __raw_spin_lock_irqsave(&object->lock:0) > [W] _raw_spin_lock_nested(&object->lock:0) > [E] spin_unlock(&object->lock:0) > > [S] __raw_spin_lock_irqsave(&object->lock:0): > [<ffffffc00810302c>] scan_gray_list+0x84/0x13c > stacktrace: > dept_ecxt_enter+0x88/0xf4 > _raw_spin_lock_irqsave+0xf0/0x1c4 > scan_gray_list+0x84/0x13c > kmemleak_scan+0x2d8/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 [W]'s stack trace is missed. But I guess this issue is the same issue of what you reported following this one. We can discuss this issue on the other report's thread. Thanks, Byunghcul > [E] spin_unlock(&object->lock:0): > [<ffffffc008102ee0>] scan_block+0x60/0x128 > --------------------------------------------------- > information that might be helpful > --------------------------------------------------- > CPU: 1 PID: 38 Comm: kmemleak Tainted: G W 5.17.0-rc1+ #1 > Hardware name: linux,dummy-virt (DT) > Call trace: > dump_backtrace.part.0+0x9c/0xc4 > show_stack+0x14/0x28 > dump_stack_lvl+0x9c/0xcc > dump_stack+0x14/0x2c > print_circle+0x2d4/0x438 > cb_check_dl+0x44/0x70 > bfs+0x60/0x168 > add_dep+0x88/0x11c > add_wait+0x2d0/0x2dc > __dept_wait+0x8c/0xa4 > dept_wait+0x6c/0x88 > _raw_spin_lock_nested+0xa8/0x1b0 > scan_block+0xb4/0x128 > scan_gray_list+0xc4/0x13c > kmemleak_scan+0x2d8/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 > > > --- > > > > Hi Linus and folks, > > > > I've been developing a tool for detecting deadlock possibilities by > > tracking wait/event rather than lock(?) acquisition order to try to > > cover all synchonization machanisms. It's done on v5.17-rc1 tag. > > > > https://github.com/lgebyungchulpark/linux-dept/commits/dept1.14_on_v5.17-rc1 > > > [...] > > Benifit: > > > > 0. Works with all lock primitives. > > 1. Works with wait_for_completion()/complete(). > > 2. Works with 'wait' on PG_locked. > > 3. Works with 'wait' on PG_writeback. > > 4. Works with swait/wakeup. > > 5. Works with waitqueue. > > 6. Multiple reports are allowed. > > 7. Deduplication control on multiple reports. > > 8. Withstand false positives thanks to 6. > > 9. Easy to tag any wait/event. > > > > Future work: > > > > 0. To make it more stable. > > 1. To separates Dept from Lockdep. > > 2. To improves performance in terms of time and space. > > 3. To use Dept as a dependency engine for Lockdep. > > 4. To add any missing tags of wait/event in the kernel. > > 5. To deduplicate stack trace. > > > > How to interpret reports: > > > > 1. E(event) in each context cannot be triggered because of the > > W(wait) that cannot be woken. > > 2. The stack trace helping find the problematic code is located > > in each conext's detail. > > > > Thanks, > > Byungchul > > > > --- > > > > Changes from v2: > > > > 1. Disable Dept on bit_wait_table[] in sched/wait_bit.c > > reporting a lot of false positives, which is my fault. > > Wait/event for bit_wait_table[] should've been tagged in a > > higher layer for better work, which is a future work. > > (feedback from Jan Kara) > > 2. Disable Dept on crypto_larval's completion to prevent a false > > positive. > > > > Changes from v1: > > > > 1. Fix coding style and typo. (feedback from Steven) > > 2. Distinguish each work context from another in workqueue. > > 3. Skip checking lock acquisition with nest_lock, which is about > > correct lock usage that should be checked by Lockdep. > > > > Changes from RFC: > > > > 1. Prevent adding a wait tag at prepare_to_wait() but __schedule(). > > (feedback from Linus and Matthew) > > 2. Use try version at lockdep_acquire_cpus_lock() annotation. > > 3. Distinguish each syscall context from another. > [ ... ] > > -- > Thank you, You are awesome! > Hyeonggon :-)
