On Wed, Mar 02, 2022 at 04:53:41AM +0000, Hyeonggon Yoo wrote: > 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? > > > > Forgot to include another warning caused by DEPT. > > And comment below might be useful for debugging: > > in kmemleak.c: > 43 * Locks and mutexes are acquired/nested in the following order: > 44 * > 45 * scan_mutex [-> object->lock] -> kmemleak_lock -> other_object->lock (SINGLE_DEPTH_NESTING) > 46 * > 47 * No kmemleak_lock and object->lock nesting is allowed outside scan_mutex > 48 * regions. > > =================================================== > DEPT: Circular dependency has been detected. > 5.17.0-rc1+ #1 Tainted: G W > --------------------------------------------------- > summary > --------------------------------------------------- > *** DEADLOCK *** > > context A > [S] __raw_spin_lock_irqsave(&object->lock:0) > [W] __raw_spin_lock_irqsave(kmemleak_lock:0) > [E] spin_unlock(&object->lock:0) > > context B > [S] __raw_spin_lock_irqsave(kmemleak_lock:0) > [W] _raw_spin_lock_nested(&object->lock:0) > [E] spin_unlock(kmemleak_lock:0) > > [S]: start of the event context > [W]: the wait blocked > [E]: the event not reachable Hi Hyeonggon, Dept also allows the following scenario when an user guarantees that each lock instance is different from another at a different depth: lock A0 with depth lock A1 with depth + 1 lock A2 with depth + 2 lock A3 with depth + 3 (and so on) .. unlock A3 unlock A2 unlock A1 unlock A0 However, Dept does not allow the following scenario where another lock class cuts in the dependency chain: lock A0 with depth lock B lock A1 with depth + 1 lock A2 with depth + 2 lock A3 with depth + 3 (and so on) .. unlock A3 unlock A2 unlock A1 unlock B unlock A0 This scenario is clearly problematic. What do you think is going to happen with another context running the following? lock A1 with depth lock B lock A2 with depth + 1 lock A3 with depth + 2 (and so on) .. unlock A3 unlock A2 unlock B unlock A1 It's a deadlock. That's why Dept reports this case as a problem. Or am I missing something? Thanks, Byungchul > --------------------------------------------------- > context A's detail > --------------------------------------------------- > context A > [S] __raw_spin_lock_irqsave(&object->lock:0) > [W] __raw_spin_lock_irqsave(kmemleak_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] __raw_spin_lock_irqsave(kmemleak_lock:0): > [<ffffffc008102ebc>] scan_block+0x3c/0x128 > stacktrace: > __dept_wait+0x8c/0xa4 > dept_wait+0x6c/0x88 > _raw_spin_lock_irqsave+0xb8/0x1c4 > scan_block+0x3c/0x128 > scan_gray_list+0xc4/0x13c > kmemleak_scan+0x2d8/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 > > [E] spin_unlock(&object->lock:0): > [<ffffffc008102ee0>] scan_block+0x60/0x128 > > --------------------------------------------------- > context B's detail > --------------------------------------------------- > context B > [S] __raw_spin_lock_irqsave(kmemleak_lock:0) > [W] _raw_spin_lock_nested(&object->lock:0) > [E] spin_unlock(kmemleak_lock:0) > > [S] __raw_spin_lock_irqsave(kmemleak_lock:0): > [<ffffffc008102ebc>] scan_block+0x3c/0x128 > stacktrace: > dept_ecxt_enter+0x88/0xf4 > _raw_spin_lock_irqsave+0xf0/0x1c4 > scan_block+0x3c/0x128 > kmemleak_scan+0x19c/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 > > [W] _raw_spin_lock_nested(&object->lock:0): > [<ffffffc008102f34>] scan_block+0xb4/0x128 > stacktrace: > dept_wait+0x74/0x88 > _raw_spin_lock_nested+0xa8/0x1b0 > scan_block+0xb4/0x128 > kmemleak_scan+0x19c/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 > [E] spin_unlock(kmemleak_lock:0): > [<ffffffc008102ee0>] scan_block+0x60/0x128 > stacktrace: > dept_event+0x7c/0xfc > _raw_spin_unlock_irqrestore+0x8c/0x120 > scan_block+0x60/0x128 > kmemleak_scan+0x19c/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 > --------------------------------------------------- > 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+0x6c/0x70 > bfs+0xc0/0x168 > add_dep+0x88/0x11c > add_wait+0x2d0/0x2dc > __dept_wait+0x8c/0xa4 > dept_wait+0x6c/0x88 > _raw_spin_lock_irqsave+0xb8/0x1c4 > scan_block+0x3c/0x128 > scan_gray_list+0xc4/0x13c > kmemleak_scan+0x2d8/0x54c > kmemleak_scan_thread+0xac/0xd4 > kthread+0xd4/0xe4 > ret_from_fork+0x10/0x20 > > > =================================================== > > 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 > > > > [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 > > > [...] > > -- > Thank you, You are awesome! > Hyeonggon :-)
