linux-kernel - Re: [Query] Preemption (hogging) of the work handler

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Date:	Wed, 13 Jul 2016 16:00:04 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Petr Mladek <pmladek@...e.com>, rjw@...ysocki.net,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Jan Kara <jack@...e.cz>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Tejun Heo <tj@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	vlevenetz@...sol.com, vaibhav.hiremath@...aro.org,
	alex.elder@...aro.org, johan@...nel.org, akpm@...ux-foundation.org,
	rostedt@...dmis.org, linux-pm@...r.kernel.org
Subject: Re: [Query] Preemption (hogging) of the work handler

On (07/12/16 10:11), Viresh Kumar wrote:
> +extern bool printk_sync_suspended;
>  static int suspend_enter(suspend_state_t state, bool *wakeup)
>  {
>         char suspend_abort[MAX_SUSPEND_ABORT_LEN];
> @@ -218,6 +219,7 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>         }
>  
>         arch_suspend_disable_irqs();
> +       printk_sync_suspended = true;
>         BUG_ON(!irqs_disabled());
>  
>         error = syscore_suspend();
> @@ -237,6 +239,7 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>                 syscore_resume();
>         }
>  
> +       printk_sync_suspended = false;
>         arch_suspend_enable_irqs();
>         BUG_ON(irqs_disabled());
>  
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 46bb017ac2c9..187054074b96 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -293,6 +293,7 @@ static u32 log_buf_len = __LOG_BUF_LEN;
>  
>  /* Control whether printing to console must be synchronous. */
>  static bool __read_mostly printk_sync = false;
> +bool printk_sync_suspended = false;
>  /* Printing kthread for async printk */
>  static struct task_struct *printk_kthread;
>  /* When `true' printing thread has messages to print */
> @@ -300,7 +301,7 @@ static bool printk_kthread_need_flush_console;
>  
>  static inline bool can_printk_async(void)
>  {
> -       return !printk_sync && printk_kthread;
> +       return !printk_sync && !printk_sync_suspended && printk_kthread;
>  }
>  
>  /* Return log buffer address */
> 
> 
> i.e. I disabled async-printk after interrupts are disabled on the last
> running CPU (0) and enabled it again before enabling interrupts back.
> 
> This FIXES the hangs for me :)

ah, just saw this. OK, very close to what I sent in another thread, so I
guess it will work on your side.
let me know if it doesn't, I'll fold it into 0001 and re-spin the series.
thanks for your help!


I'll also drop the KERN_CONT patch for now. apparently it didn't work for
Petr.

	-ss