linux-kernel - Re: [PATCH] printk: modify console

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Message-ID: <CAOVJa8FWC=wJ_2SVbvJBkotWpzpNaOqJ_8Fb+4=oUbb+AHJttg@mail.gmail.com>
Date:   Mon, 17 Jul 2017 19:06:18 +0800
From:   pierre kuo <vichy.kuo@...il.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        rostedt@...dmis.org, linux-kernel@...r.kernel.org,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] printk: modify console_unlock with printk-safe macros

hi Sergey and Andy:
> On (07/15/17 18:36), Pierre Kuo wrote:
> [..]
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index fc47863..21557cc 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -2194,8 +2194,7 @@ void console_unlock(void)
>>               size_t ext_len = 0;
>>               size_t len;
>>
>> -             printk_safe_enter_irqsave(flags);
>> -             raw_spin_lock(&logbuf_lock);
>> +             logbuf_lock_irqsave(flags);
>>               if (seen_seq != log_next_seq) {
>>                       wake_klogd = true;
>>                       seen_seq = log_next_seq;
>> @@ -2267,8 +2266,7 @@ void console_unlock(void)
>>        */
>>       raw_spin_lock(&logbuf_lock);
>>       retry = console_seq != log_next_seq;
>> -     raw_spin_unlock(&logbuf_lock);
>> -     printk_safe_exit_irqrestore(flags);
>> +     logbuf_unlock_irqrestore(flags);
>>
>>       if (retry && console_trylock())
>>               goto again;
>
> I did it that particular way for a reason - console_unlock() does a
> bunch of tricks: unlocking logbuf in the middle of printing loop,
> breaking out of loop with local IRQs disabled, re-taking the logbuf
> after the loop still will local IRQs disabled, etc. etc. I didn't
> want to (and still don't) mix-in logbuf macros; we do things that
> macros don't cover anyway. sorry, I don't agree that the patch
> improves readability.
Got ur points and appreciate for your illustration. ^^
Thanks a lot,