Messages in this thread | | | Date | Fri, 12 Nov 2021 10:41:55 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH v2 1/1] printk: suppress rcu stall warnings caused by slow console devices |
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On (21/11/11 16:59), Wander Lairson Costa wrote: > > If we have a reasonable large dataset to flush in the printk ring > buffer in the presence of a slow console device (like a serial port > with a low baud rate configured), the RCU stall detector may report > warnings. > > This patch suppresses RCU stall warnings while flushing the ring buffer > to the console. > [..] > +extern int rcu_cpu_stall_suppress; > + > +static void rcu_console_stall_suppress(void) > +{ > + if (!rcu_cpu_stall_suppress) > + rcu_cpu_stall_suppress = 4; > +} > + > +static void rcu_console_stall_unsuppress(void) > +{ > + if (rcu_cpu_stall_suppress == 4) > + rcu_cpu_stall_suppress = 0; > +} > + > /** > * console_unlock - unlock the console system > * > @@ -2634,6 +2648,9 @@ void console_unlock(void) > * and cleared after the "again" goto label. > */ > do_cond_resched = console_may_schedule; > + > + rcu_console_stall_suppress(); > + > again: > console_may_schedule = 0; > > @@ -2645,6 +2662,7 @@ void console_unlock(void) > if (!can_use_console()) { > console_locked = 0; > up_console_sem(); > + rcu_console_stall_unsuppress(); > return; > } > > @@ -2716,8 +2734,10 @@ void console_unlock(void) > > handover = console_lock_spinning_disable_and_check(); > printk_safe_exit_irqrestore(flags); > - if (handover) > + if (handover) { > + rcu_console_stall_unsuppress(); > return; > + } > > if (do_cond_resched) > cond_resched(); > @@ -2738,6 +2758,8 @@ void console_unlock(void) > retry = prb_read_valid(prb, next_seq, NULL); > if (retry && console_trylock()) > goto again; > + > + rcu_console_stall_unsuppress(); > }
May be we can just start touching watchdogs from printing routine?
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