Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 18 Apr 2024 22:38:49 +0530 | Subject | Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue | From | K Prateek Nayak <> |
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Hello Mike,
On 4/18/2024 9:54 PM, Mike Galbraith wrote: > Greetings, > > I tossed a couple rocks at it today, and seem to have hit the little > bugger. The root cause seems to be doing the delay dequeue business on > exiting tasks. Hunk #1 of hacklet below seems to quell the explosions. > > crash> bt -sx > PID: 21722 TASK: ffff88815710ee40 CPU: 6 COMMAND: "hackbench" > #0 [ffff88822773bb90] machine_kexec+0x156 at ffffffff810642d6 > #1 [ffff88822773bbe0] __crash_kexec+0xd7 at ffffffff81152a07 > #2 [ffff88822773bc98] crash_kexec+0x23 at ffffffff81152eb3 > #3 [ffff88822773bca8] oops_end+0xbe at ffffffff810329be > #4 [ffff88822773bcc8] page_fault_oops+0x81 at ffffffff81071951 > #5 [ffff88822773bd28] exc_page_fault+0x62 at ffffffff8194e9e2 > #6 [ffff88822773bd50] asm_exc_page_fault+0x22 at ffffffff81a00ba2 > [exception RIP: pick_next_task_fair+178] > RIP: ffffffff810d8d12 RSP: ffff88822773be00 RFLAGS: 00010006 > RAX: ffff88813cb780b8 RBX: ffff88840edb0e80 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: ffff88813cb78080 RDI: ffff88840ec30f00 > RBP: ffff88813cb78000 R8: ffff88815710eec0 R9: 0000000000000001 > R10: ffff88822773bdc8 R11: 0000000000000013 R12: 0000000000030e80 > R13: ffff88815710ee40 R14: ffff88813cb78080 R15: ffff88815710ee40 > ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 > #7 [ffff88822773be28] __schedule+0x10d at ffffffff8195865d > #8 [ffff88822773be98] do_task_dead+0x3e at ffffffff810cc00e > #9 [ffff88822773beb0] do_exit+0x770 at ffffffff8108f0e0 > #10 [ffff88822773bf00] do_group_exit+0x2c at ffffffff8108f64c > #11 [ffff88822773bf28] __x64_sys_exit_group+0x14 at ffffffff8108f6f4 > #12 [ffff88822773bf30] do_syscall_64+0x57 at ffffffff8194ac37 > #13 [ffff88822773bf50] entry_SYSCALL_64_after_hwframe+0x76 at ffffffff81a0012b > RIP: 00007f4f2aa76136 RSP: 00007ffcbba84748 RFLAGS: 00000246 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4f2aa76136 > RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 > RBP: 00007f4f2ab86970 R8: 00000000000000e7 R9: ffffffffffffff80 > R10: 0000000000000004 R11: 0000000000000246 R12: 00007f4f2ab86970 > R13: 0000000000000001 R14: 00007f4f2ab8a328 R15: 0000000000000000 > ORIG_RAX: 00000000000000e7 CS: 0033 SS: 002b > crash> task_struct ffff88815710ee40 | grep sched_delayed > sched_delayed = 1 '\001', > crash> >
My machine too survived the spawn test with the below patch. Thank you for looking into this. I'll resume testing with the below patch included.
-- Thanks and Regards, Prateek
> --- > kernel/sched/fair.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5374,6 +5374,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, st > update_curr(cfs_rq); > > if (sched_feat(DELAY_DEQUEUE) && sleep && > + !(entity_is_task(se) && (task_of(se)->flags & PF_EXITING)) && > !entity_eligible(cfs_rq, se)) { > if (cfs_rq->next == se) > cfs_rq->next = NULL; > @@ -5495,14 +5496,14 @@ pick_next_entity(struct rq *rq, struct c > } > > struct sched_entity *se = pick_eevdf(cfs_rq); > - if (se->sched_delayed) { > + while (se && se->sched_delayed) { > dequeue_entities(rq, se, DEQUEUE_SLEEP | DEQUEUE_DELAYED); > SCHED_WARN_ON(se->sched_delayed); > SCHED_WARN_ON(se->on_rq); > if (sched_feat(DELAY_ZERO) && se->vlag > 0) > se->vlag = 0; > > - return NULL; > + se = pick_eevdf(cfs_rq); > } > return se; > } >
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