On Thu, Nov 14, 2024 at 10:16:12AM -0800, Paul E. McKenney wrote: > On Mon, Oct 21, 2024 at 12:25:41PM -0700, Paul E. McKenney wrote: > > On Mon, Oct 14, 2024 at 11:55:05AM -0700, Paul E. McKenney wrote: > > [ . . . ] > > > > But no big wins thus far, so this will be a slow process. My current test > > > disables CPU hotplug. I will be disabling other things in the hope of > > > better identifying the code paths that should be placed under suspicion. > > The "this will be a slow process" was no joke... [ . . . ] > Back to beating on it. More info than anyone needs is available here: > > https://docs.google.com/document/d/1-JQ4QYF1qid0TWSLa76O1kusdhER2wgm0dYdwFRUzU8/edit?usp=sharing And the fix for the TREE03 too-short grace periods is finally in, at least in prototype form: https://lore.kernel.org/all/da5065c4-79ba-431f-9d7e-1ca314394443@paulmck-laptop/ Or this commit on -rcu: 22bee20913a1 ("rcu: Fix get_state_synchronize_rcu_full() GP-start detection") This passes more than 30 hours of 400 concurrent instances of rcutorture's TREE03 scenario, with modifications that brought the bug reproduction rate up to 50 per hour. I therefore have strong reason to believe that this fix is a real fix. With this fix in place, a 20-hour run of 400 concurrent instances of rcutorture's TREE03 scenario resulted in 50 instances of the enqueue_dl_entity() splat pair. One (untrimmed) instance of this pair of splats is shown below. You guys did reproduce this some time back, so unless you tell me otherwise, I will assume that you have this in hand. I would of course be quite happy to help, especially with adding carefully chosen debug (heisenbug and all that) or testing of alleged fixes. Just let me know! Thanx, Paul ------------------------------------------------------------------------ ------------[ cut here ]------------ smpboot: Booting Node 0 Processor 3 APIC 0x3 WARNING: CPU: 1 PID: 29304 at kernel/sched/deadline.c:1995 enqueue_dl_entity+0x511/0x5d0 Modules linked in: CPU: 1 UID: 0 PID: 29304 Comm: kworker/1:2 Not tainted 6.13.0-rc1-00063-ga51301a307ab-dirty #2355 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 Workqueue: rcu_gp sync_rcu_do_polled_gp RIP: 0010:enqueue_dl_entity+0x511/0x5d0 Code: ff 48 89 ef e8 10 cf ff ff 0f b6 4d 54 e9 0e fc ff ff 85 db 0f 84 d0 fe ff ff 5b 44 89 e6 48 89 ef 5d 41 5c e9 30 d6 ff ff 90 <0f> 0b 90 e9 fa fa ff ff 48 8b bb f8 09 00 00 48 39 fe 0f 89 de fb RSP: 0018:ffff9b88c13ebaf0 EFLAGS: 00010086 RAX: 0000000000000001 RBX: ffff893a5f4ac8e8 RCX: 0000000000000002 RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff893a5f4ac8e8 RBP: ffff893a5f4ac8e8 R08: 0000000000000001 R09: 0000000000000197 R10: 0000000000000000 R11: ffff893a4181bb90 R12: 0000000000000001 R13: 000000000016e360 R14: ffff893a5f4ac040 R15: ffff893a5f4ac080 FS: 0000000000000000(0000) GS:ffff893a5f480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000001d06000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? __warn+0x83/0x130 ? enqueue_dl_entity+0x511/0x5d0 ? report_bug+0x18e/0x1a0 ? handle_bug+0x54/0x90 ? exc_invalid_op+0x18/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? enqueue_dl_entity+0x511/0x5d0 dl_server_start+0x31/0xe0 enqueue_task_fair+0x21b/0x6b0 enqueue_task+0x2c/0x70 activate_task+0x21/0x50 attach_task+0x30/0x50 sched_balance_rq+0x654/0xdf0 sched_balance_newidle.constprop.0+0x190/0x360 pick_next_task_fair+0x2a/0x340 __schedule+0x1f3/0x8f0 schedule+0x22/0xd0 synchronize_rcu_expedited+0x1bf/0x350 ? __pfx_autoremove_wake_function+0x10/0x10 ? __pfx_wait_rcu_exp_gp+0x10/0x10 sync_rcu_do_polled_gp+0x4f/0x110 process_one_work+0x163/0x390 worker_thread+0x293/0x3b0 ? __pfx_worker_thread+0x10/0x10 kthread+0xd1/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2f/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> ---[ end trace 0000000000000000 ]--- ------------[ cut here ]------------ WARNING: CPU: 1 PID: 29304 at kernel/sched/deadline.c:1971 enqueue_dl_entity+0x54f/0x5d0 Modules linked in: CPU: 1 UID: 0 PID: 29304 Comm: kworker/1:2 Tainted: G W 6.13.0-rc1-00063-ga51301a307ab-dirty #2355 Tainted: [W]=WARN Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 Workqueue: rcu_gp sync_rcu_do_polled_gp RIP: 0010:enqueue_dl_entity+0x54f/0x5d0 Code: de fb ff ff e9 66 ff ff ff 89 c1 45 84 d2 0f 84 ce fb ff ff a8 20 0f 84 c6 fb ff ff 84 c0 0f 89 20 fe ff ff e9 b9 fb ff ff 90 <0f> 0b 90 e9 f4 fb ff ff 84 d2 0f 85 e3 fa ff ff 48 89 ea 48 8d b5 RSP: 0018:ffff9b88c13ebaf0 EFLAGS: 00010086 RAX: 00000000ffffff00 RBX: ffff893a5f4ac040 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000b1a2986b8 RDI: 0000000b1a268bc8 RBP: ffff893a5f4ac8e8 R08: ffff893a5f4ac880 R09: 000000003b9aca00 R10: 0000000000000001 R11: 00000000000ee6b2 R12: 0000000000000001 R13: 000000000016e360 R14: ffff893a5f4ac040 R15: ffff893a5f4ac080 FS: 0000000000000000(0000) GS:ffff893a5f480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000001d06000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? __warn+0x83/0x130 ? enqueue_dl_entity+0x54f/0x5d0 ? report_bug+0x18e/0x1a0 ? handle_bug+0x54/0x90 ? exc_invalid_op+0x18/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? enqueue_dl_entity+0x54f/0x5d0 dl_server_start+0x31/0xe0 enqueue_task_fair+0x21b/0x6b0 enqueue_task+0x2c/0x70 activate_task+0x21/0x50 attach_task+0x30/0x50 sched_balance_rq+0x654/0xdf0 sched_balance_newidle.constprop.0+0x190/0x360 pick_next_task_fair+0x2a/0x340 __schedule+0x1f3/0x8f0 schedule+0x22/0xd0 synchronize_rcu_expedited+0x1bf/0x350 ? __pfx_autoremove_wake_function+0x10/0x10 ? __pfx_wait_rcu_exp_gp+0x10/0x10 sync_rcu_do_polled_gp+0x4f/0x110 process_one_work+0x163/0x390 worker_thread+0x293/0x3b0 ? __pfx_worker_thread+0x10/0x10 kthread+0xd1/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2f/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> ---[ end trace 0000000000000000 ]---
