Messages in this thread | | | Subject | Re: [PATCH] printk: stop spining waiter when console resume to flush prb | From | luojiaxing <> | Date | Fri, 7 May 2021 15:58:31 +0800 |
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On 2021/5/6 23:14, John Ogness wrote: > On 2021-05-06, Sergey Senozhatsky <senozhatsky@chromium.org> wrote: >>> Can we count the number of lines that we print from the `current` context >>> in console_unlock() and if after N messages there is no console_lock waiter >>> waiting for the `current` to handover console lock ownership, then create >>> one: schedule IRQ work that will become a console lock owner, spin on >>> console lock and call console_unlock() once it acquired the ownership. >>> That 'artificial' console lock owner will do the same - print N >>> messages, if nothing wants to become a console lock owner then it'll >>> queue another IRQ work. >> Or even simpler >> >> console_unlock() >> { >> ... >> >> if (printed_messages > limit && !console_lock_spinning_disable_and_check()) { >> printk_safe_exit_irqrestore(flags); >> >> console_locked = 0; >> up_console_sem(); >> >> defer_console_output(); >> return; >> } >> >> ... >> } > Or instead to keep it suspend/resume related maybe... > > void resume_console(void) > { > if (!console_suspend_enabled) > return; > down_console_sem(); > console_suspended = 0; > - console_unlock(); > + console_locked = 0; > + up_console_sem(); > + defer_console_output();
Hi, john, I test this and found a calltrace below:
[ 467.670366] hisi_sas_v3_hw 0000:b4:02.0: print test [ 467.670367] hisi_sas_v3_hw 0000:b4:02.0: print test [ 467.670368] hisi_sas_v3_hw 0000:b4:02.0: print test [ 467.670369] hisi_sas_v3_hw 0000:b4:02.0: print test [ 467.670370] hisi_sas_v3_hw 0000:b4:02.0: print test [ 467.670371] hisi_sas_v3_hw 0000:b4:02.0: print test [ 468.297467] hisi_sas_v3_hw 0000:b4:02.0: print test [ 489.298709] rcu: INFO: rcu_preempt self-detected stall on CPU [ 489.298712] rcu: 44-....: (4324 ticks this GP) idle=e6e/1/0x4000000000000002 softirq=1212/1212 fqs=2625 [ 489.298722] (t=5250 jiffies g=3285 q=1820) [ 489.298725] Task dump for CPU 44: [ 489.298726] task:bash state:R running task stack: 0 pid:16937 ppid: 16935 flags:0x00000206 [ 489.298731] Call trace: [ 489.298732] dump_backtrace+0x0/0x1a4 [ 489.298738] show_stack+0x24/0x40 [ 489.298740] sched_show_task+0x148/0x170 [ 489.298744] dump_cpu_task+0x50/0x60 [ 489.298748] rcu_dump_cpu_stacks+0x10c/0x154 [ 489.298751] rcu_sched_clock_irq+0x8d4/0xd94 [ 489.298755] update_process_times+0xa8/0xf4 [ 489.298758] tick_sched_handle+0x38/0x74 [ 489.298760] tick_sched_timer+0x58/0xb0 [ 489.298762] __hrtimer_run_queues+0x18c/0x3a0 [ 489.298764] hrtimer_interrupt+0xf4/0x2cc [ 489.298767] arch_timer_handler_phys+0x40/0x50 [ 489.298771] handle_percpu_devid_irq+0x94/0x280 [ 489.298775] __handle_domain_irq+0x88/0xf0 [ 489.298777] gic_handle_irq+0xd8/0x2c0 [ 489.298779] el1_irq+0xbc/0x180 [ 489.298780] console_unlock+0x390/0x580 [ 489.298782] vprintk_emit+0x104/0x280 [ 489.298784] dev_vprintk_emit+0x14c/0x184 [ 489.298787] dev_printk_emit+0x64/0x8c [ 489.298789] __dev_printk+0x60/0x84 [ 489.298792] _dev_info+0x6c/0x94 [ 489.298794] debugfs_test_if_1_write+0xc0/0x14c [hisi_sas_v3_hw] [ 489.298801] full_proxy_write+0x6c/0xc0 [ 489.298804] vfs_write+0xfc/0x2b0 [ 489.298807] ksys_write+0x74/0x100 [ 489.298809] __arm64_sys_write+0x28/0x34 [ 489.298812] el0_svc_common.constprop.0+0x70/0x1a4 [ 489.298815] do_el0_svc+0x28/0x3c [ 489.298817] el0_svc+0x2c/0x70 [ 489.298820] el0_sync_handler+0x1a4/0x1b0 [ 489.298822] el0_sync+0x170/0x180 [ 492.474266] hisi_sas_v3_hw 0000:b4:02.0: print test [ 492.479137] hisi_sas_v3_hw 0000:b4:02.0: print test [ 492.483996] hisi_sas_v3_hw 0000:b4:02.0: print test [ 492.488857] hisi_sas_v3_hw 0000:b4:02.0: print test [ 492.493716] hisi_sas_v3_hw 0000:b4:02.0: print test [ 492.498574] hisi_sas_v3_hw 0000:b4:02.0: print test
My test method is as follows: Use a kernel thread to make the console enter suspend, sleep for 10 seconds, and then resume.
At the same time, another thread repeatedly calls printk() for output.
Thanks
Jiaxing
> } > > John Ogness > > . >
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