On (04/08/16 02:31), Sergey Senozhatsky wrote:
> Hello,
>
> This patch set makes printk() completely asynchronous: new messages
> are getting upended to the kernel printk buffer, but instead of 'direct'
> printing the actual print job is performed by a dedicated kthread.
> This has the advantage that printing always happens from a schedulable
> context and thus we don't lockup any particular CPU or even interrupts.
Hello,
Sir, is there anything else you want me to improve in this patch set?
-ss
> against next-20160407
>
> v11:
> -- switch default to sync printk
> -- make `synchronous' param RW (Andrew, Jan)
> -- set RT priority to printk kthread (Andrew)
> -- correct comments (Andrew)
>
> v10:
> -- simplify printk_kthread_need_flush_console (Jan, Petr)
>
> v9:
> -- move need_flush_console assignment down in vprintk_emit (Jan)
> -- simplify need_flush_console assignment rules (Petr)
> -- clear need_flush_console in printing function (Petr)
> -- rename need_flush_console (Petr)
>
> v8:
> -- rename kthread printing function (Petr)
> -- clear need_flush_console in console_unlock() under logbuf (Petr)
>
> v7:
> -- do not set global printk_sync in panic in vrintk_emit() (Petr)
> -- simplify vprintk_emit(). drop some of local variables (Petr)
> -- move handling of LOGLEVEL_SCHED messages back to printk_deferred()
> so we wake_up_process()/console_trylock() in vprintk_emit() only
> for !in_sched messages
>
> v6:
> -- move wake_up_process out of logbuf lock (Jan, Byungchul)
> -- do not disable async printk in recursion handling code.
> -- rebase against next-20160321 (w/NMI patches)
>
> v5:
> -- make printk.synchronous RO (Petr)
> -- make printing_func() correct and do not use wait_queue (Petr)
> -- do not panic() when can't allocate printing thread (Petr)
> -- do not wake_up_process() only in IRQ, prefer vprintk_emit() (Jan)
> -- move wake_up_klogd_work_func() to a separate patch (Petr)
> -- move wake_up_process() under logbuf lock so printk recursion logic can
> help us out
> -- switch to sync_print mode if printk recursion occured
> -- drop "printk: Skip messages on oops" patch
>
> v4:
> -- do not directly wake_up() the printing kthread from vprintk_emit(), need
> to go via IRQ->wake_up() to avoid sched deadlocks (Jan)
>
> v3:
> -- use a dedicated kthread for printing instead of using wq (Jan, Tetsuo,
> Tejun)
>
> v2:
> - use dedicated printk workqueue with WQ_MEM_RECLAIM bit
> - fallback to system-wide workqueue only if allocation of printk_wq has
> failed
> - do not use system_wq as a fallback wq. both console_lock() and
> onsole_unlock()
> can spend a significant amount of time; so we need to use system_long_wq.
> - rework sync/!sync detection logic
> a) we can have deferred (in_sched) messages before we allocate printk_wq,
> so the only way to handle those messages is via IRQ context
> b) even in printk.synchronous mode, deferred messages must not be printed
> directly, and should go via IRQ context
> c) even if we allocated printk_wq and have !sync_printk mode, we must route
> deferred messages via IRQ context
> - so this adds additional bool flags to vprint_emit() and introduces a new
> pending bit to `printk_pending'
> - fix build on !PRINTK configs
>
>
> Jan Kara (2):
> printk: Make printk() completely async
> printk: Make wake_up_klogd_work_func() async
>
> Sergey Senozhatsky (1):
> printk: make printk.synchronous param rw
>
> Documentation/kernel-parameters.txt | 12 +++
> kernel/printk/printk.c | 155
> +++++++++++++++++++++++++++++++++---
> 2 files changed, 157 insertions(+), 10 deletions(-)
>
> --
> 2.8.0
>
