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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJZ5v0gPJ9XOHO3xbbt+irPfh_V72-jeV8L_OTmA=8xnFbVmbQ@mail.gmail.com>
Date:	Wed, 13 Jul 2016 14:05:19 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	Petr Mladek <pmladek@...e.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, 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,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [Query] Preemption (hogging) of the work handler

On Wed, Jul 13, 2016 at 9:00 AM, Sergey Senozhatsky
<sergey.senozhatsky.work@...il.com> wrote:
> 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!

But you need to do an analogous thing for hibernation.  Essentially,
wherever disable_nonboot_cpus() is called.

Thanks,
Rafael