On Wed, Mar 16, 2022 at 01:32:13PM +0900, Byungchul Park wrote: > On Sat, Mar 12, 2022 at 01:53:26AM +0000, Hyeonggon Yoo wrote: > > On Fri, Mar 04, 2022 at 04:06:19PM +0900, Byungchul Park wrote: > > > 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 > > > > > > > Small feedback unrelated to thread: > > I'm not sure "Need to expand the ring buffer" is something to call > > WARN(). Is this stack trace useful for something? > > ======== > > > > Hello Byungchul. These are two warnings of DEPT on system. > > Hi Hyeonggon, > > Could you run scripts/decode_stacktrace.sh and share the result instead > of the raw format below if the reports still appear with PATCH v5? It'd > be appreciated (: > Hi Byungchul. on dept1.18_on_v5.17-rc7, the kernel_clone() warning has gone. There is one warning remaining on my system: It warns when running kunit-try-catch-test testcase. =================================================== DEPT: Circular dependency has been detected. 5.17.0-rc7+ #4 Not tainted --------------------------------------------------- summary --------------------------------------------------- *** AA DEADLOCK *** context A [S] (unknown)(&try_completion:0) [W] wait_for_completion_timeout(&try_completion:0) [E] complete(&try_completion:0) [S]: start of the event context [W]: the wait blocked [E]: the event not reachable --------------------------------------------------- context A's detail --------------------------------------------------- context A [S] (unknown)(&try_completion:0) [W] wait_for_completion_timeout(&try_completion:0) [E] complete(&try_completion:0) [S] (unknown)(&try_completion:0): (N/A) [W] wait_for_completion_timeout(&try_completion:0): kunit_try_catch_run (lib/kunit/try-catch.c:78 (discriminator 1)) stacktrace: dept_wait (kernel/dependency/dept.c:2149) wait_for_completion_timeout (kernel/sched/completion.c:119 (discriminator 4) kernel/sched/completion.c:165 (discriminator 4)) kunit_try_catch_run (lib/kunit/try-catch.c:78 (discriminator 1)) kunit_test_try_catch_successful_try_no_catch (lib/kunit/kunit-test.c:43) kunit_try_run_case (lib/kunit/test.c:333 lib/kunit/test.c:374) kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:30) kthread (kernel/kthread.c:379) ret_from_fork (arch/arm64/kernel/entry.S:757) [E] complete(&try_completion:0): kthread_complete_and_exit (kernel/kthread.c:327) stacktrace: dept_event (kernel/dependency/dept.c:2376 (discriminator 2)) complete (kernel/sched/completion.c:33 (discriminator 4)) kthread_complete_and_exit (kernel/kthread.c:327) kunit_try_catch_throw (lib/kunit/try-catch.c:18) kthread (kernel/kthread.c:379) ret_from_fork (arch/arm64/kernel/entry.S:757) --------------------------------------------------- information that might be helpful --------------------------------------------------- Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace.part.0 (arch/arm64/kernel/stacktrace.c:186) show_stack (arch/arm64/kernel/stacktrace.c:193) dump_stack_lvl (lib/dump_stack.c:107 (discriminator 4)) dump_stack (lib/dump_stack.c:114) print_circle (./arch/arm64/include/asm/atomic_ll_sc.h:112 ./arch/arm64/include/asm/atomic.h:30 ./include/linux/atomic/atomic-arch-fallback.h:511 ./include/linux/atomic/atomic-instrumented.h:258 kernel/dependency/dept.c:140 kernel/dependency/dept.c:748) cb_check_dl (kernel/dependency/dept.c:1083 kernel/dependency/dept.c:1064) bfs (kernel/dependency/dept.c:833) add_dep (kernel/dependency/dept.c:1409) do_event (kernel/dependency/dept.c:175 kernel/dependency/dept.c:1644) dept_event (kernel/dependency/dept.c:2376 (discriminator 2)) complete (kernel/sched/completion.c:33 (discriminator 4)) kthread_complete_and_exit (kernel/kthread.c:327) kunit_try_catch_throw (lib/kunit/try-catch.c:18) kthread (kernel/kthread.c:379) ret_from_fork (arch/arm64/kernel/entry.S:757) -- Thank you, You are awesome! Hyeonggon :-) > https://lkml.org/lkml/2022/3/15/1277 > (or https://github.com/lgebyungchulpark/linux-dept/commits/dept1.18_on_v5.17-rc7) > > Thank you very much! > > -- > Byungchul > > > Both cases look similar. > > > > In what case DEPT says (unknown)? > > I'm not sure we can properly debug this. > > > > =================================================== > > DEPT: Circular dependency has been detected. > > 5.17.0-rc1+ #3 Tainted: G W > > --------------------------------------------------- > > summary > > --------------------------------------------------- > > *** AA DEADLOCK *** > > > > context A > > [S] (unknown)(&vfork:0) > > [W] wait_for_completion_killable(&vfork:0) > > [E] complete(&vfork:0) > > > > [S]: start of the event context > > [W]: the wait blocked > > [E]: the event not reachable > > --------------------------------------------------- > > context A's detail > > --------------------------------------------------- > > context A > > [S] (unknown)(&vfork:0) > > [W] wait_for_completion_killable(&vfork:0) > > [E] complete(&vfork:0) > > > > [S] (unknown)(&vfork:0): > > (N/A) > > > > [W] wait_for_completion_killable(&vfork:0): > > [<ffffffc00802204c>] kernel_clone+0x25c/0x2b8 > > stacktrace: > > dept_wait+0x74/0x88 > > wait_for_completion_killable+0x60/0xa0 > > kernel_clone+0x25c/0x2b8 > > __do_sys_clone+0x5c/0x74 > > __arm64_sys_clone+0x18/0x20 > > invoke_syscall.constprop.0+0x78/0xc4 > > do_el0_svc+0x98/0xd0 > > el0_svc+0x44/0xe4 > > el0t_64_sync_handler+0xb0/0x12c > > el0t_64_sync+0x158/0x15c > > > > [E] complete(&vfork:0): > > [<ffffffc00801f49c>] mm_release+0x7c/0x90 > > stacktrace: > > dept_event+0xe0/0x100 > > complete+0x48/0x98 > > mm_release+0x7c/0x90 > > exit_mm_release+0xc/0x14 > > do_exit+0x1b4/0x81c > > do_group_exit+0x30/0x9c > > __wake_up_parent+0x0/0x24 > > invoke_syscall.constprop.0+0x78/0xc4 > > do_el0_svc+0x98/0xd0 > > el0_svc+0x44/0xe4 > > el0t_64_sync_handler+0xb0/0x12c > > el0t_64_sync+0x158/0x15c > > --------------------------------------------------- > > information that might be helpful > > --------------------------------------------------- > > CPU: 6 PID: 229 Comm: start-stop-daem Tainted: G W 5.17.0-rc1+ #3 > > 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 > > do_event.constprop.0+0x19c/0x2c0 > > dept_event+0xe0/0x100 > > complete+0x48/0x98 > > mm_release+0x7c/0x90 > > exit_mm_release+0xc/0x14 > > do_exit+0x1b4/0x81c > > do_group_exit+0x30/0x9c > > __wake_up_parent+0x0/0x24 > > invoke_syscall.constprop.0+0x78/0xc4 > > do_el0_svc+0x98/0xd0 > > el0_svc+0x44/0xe4 > > el0t_64_sync_handler+0xb0/0x12c > > el0t_64_sync+0x158/0x15c > > > > > > > > > > =================================================== > > DEPT: Circular dependency has been detected. > > 5.17.0-rc1+ #3 Tainted: G W > > --------------------------------------------------- > > summary > > --------------------------------------------------- > > *** AA DEADLOCK *** > > > > context A > > [S] (unknown)(&try_completion:0) > > [W] wait_for_completion_timeout(&try_completion:0) > > [E] complete(&try_completion:0) > > > > [S]: start of the event context > > [W]: the wait blocked > > [E]: the event not reachable > > --------------------------------------------------- > > context A's detail > > --------------------------------------------------- > > context A > > [S] (unknown)(&try_completion:0) > > [W] wait_for_completion_timeout(&try_completion:0) > > [E] complete(&try_completion:0) > > > > [S] (unknown)(&try_completion:0): > > (N/A) > > > > [W] wait_for_completion_timeout(&try_completion:0): > > [<ffffffc008166bf4>] kunit_try_catch_run+0xb4/0x160 > > stacktrace: > > dept_wait+0x74/0x88 > > wait_for_completion_timeout+0x64/0xa0 > > kunit_try_catch_run+0xb4/0x160 > > kunit_test_try_catch_successful_try_no_catch+0x3c/0x98 > > kunit_try_run_case+0x9c/0xa0 > > kunit_generic_run_threadfn_adapter+0x1c/0x28 > > kthread+0xd4/0xe4 > > ret_from_fork+0x10/0x20 > > > > [E] complete(&try_completion:0): > > [<ffffffc00803dce4>] kthread_complete_and_exit+0x18/0x20 > > stacktrace: > > dept_event+0xe0/0x100 > > complete+0x48/0x98 > > kthread_complete_and_exit+0x18/0x20 > > kunit_try_catch_throw+0x0/0x1c > > kthread+0xd4/0xe4 > > ret_from_fork+0x10/0x20 > > > > --------------------------------------------------- > > information that might be helpful > > --------------------------------------------------- > > CPU: 15 PID: 132 Comm: kunit_try_catch Tainted: G W 5.17.0-rc1+ #3 > > 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 > > do_event.constprop.0+0x19c/0x2c0 > > dept_event+0xe0/0x100 > > complete+0x48/0x98 > > kthread_complete_and_exit+0x18/0x20 > > kunit_try_catch_throw+0x0/0x1c > > kthread+0xd4/0xe4 > > ret_from_fork+0x10/0x20 > > > > > > > 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: > > > > [...] > > > > > -- > > > 1.9.1 > > > > > > > -- > > Thank you, You are awesome! > > Hyeonggon :-)
