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

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Date:	Fri, 29 Jul 2016 13:42:01 -0700
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Jan Kara <jack@...e.cz>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	rjw@...ysocki.net, 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,
	Petr Mladek <pmladek@...e.com>
Subject: Re: [Query] Preemption (hogging) of the work handler

On 13-07-16, 14:45, Sergey Senozhatsky wrote:
> something like below, perhaps. will this work for you?
> 
> ---
>  kernel/printk/printk.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index bbb4180..786690e 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -288,6 +288,11 @@ static u32 log_buf_len = __LOG_BUF_LEN;
>  
>  /* Control whether printing to console must be synchronous. */
>  static bool __read_mostly printk_sync = true;
> +/*
> + * Force sync printk mode during suspend/kexec, regardless whether
> + * console_suspend_enabled permits console suspend.
> + */
> +static bool __read_mostly force_printk_sync;
>  /* Printing kthread for async printk */
>  static struct task_struct *printk_kthread;
>  /* When `true' printing thread has messages to print */
> @@ -295,7 +300,7 @@ static bool printk_kthread_need_flush_console;
>  
>  static inline bool can_printk_async(void)
>  {
> -	return !printk_sync && printk_kthread;
> +	return !printk_sync && printk_kthread && !force_printk_sync;
>  }
>  
>  /* Return log buffer address */
> @@ -2027,6 +2032,7 @@ static bool suppress_message_printing(int level) { return false; }
>  
>  /* Still needs to be defined for users */
>  DEFINE_PER_CPU(printk_func_t, printk_func);
> +static bool __read_mostly force_printk_sync;
>  
>  #endif /* CONFIG_PRINTK */
>  
> @@ -2163,6 +2169,8 @@ MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
>   */
>  void suspend_console(void)
>  {
> +	force_printk_sync = true;
> +
>  	if (!console_suspend_enabled)
>  		return;
>  	printk("Suspending console(s) (use no_console_suspend to debug)\n");
> @@ -2173,6 +2181,8 @@ void suspend_console(void)
>  
>  void resume_console(void)
>  {
> +	force_printk_sync = false;
> +
>  	if (!console_suspend_enabled)
>  		return;
>  	down_console_sem();

I haven't seen any issues with it yet and it works just fine. Please feel free
to add below for the entire series including this hunk.

Tested-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh