linux-kernel - Re: [PATCH] kernel/async.c:introduce async_schedule*

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Date:	Tue, 12 May 2009 23:58:42 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	tom.leiming@...il.com, arjan@...radead.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] kernel/async.c:introduce async_schedule*_atomic

On Tue, May 12, 2009 at 05:44:58PM +0200, Frederic Weisbecker wrote:
>On Tue, May 12, 2009 at 11:13:42PM +0800, tom.leiming@...il.com wrote:
>> From: Ming Lei <tom.leiming@...il.com>
>> 
>> The async_schedule* may not be called in atomic contexts if out of
>> memory or if there's too much work pending already, because the
>> async function to be called may sleep.
>> 
>> This patch fixes the comment of async_schedule*, and introduces
>> async_schedules*_atomic to allow them called from atomic contexts
>> safely.
>
>
>
>Aah, great. Such helper could easily replace some workqueues
>which receive (in atomic) rare jobs but still need to exist because
>they execute jobs which take too much time to be enqueued in kevents.
>
>A good candidate: kpsmoused!
>
>
> 
>> Signed-off-by: Ming Lei <tom.leiming@...il.com>
>> ---
>>  include/linux/async.h |    3 ++
>>  kernel/async.c        |   56 ++++++++++++++++++++++++++++++++++++++++++------
>>  2 files changed, 52 insertions(+), 7 deletions(-)
>> 
>> diff --git a/include/linux/async.h b/include/linux/async.h
>> index 68a9530..ede9849 100644
>> --- a/include/linux/async.h
>> +++ b/include/linux/async.h
>> @@ -19,6 +19,9 @@ typedef void (async_func_ptr) (void *data, async_cookie_t cookie);
>>  extern async_cookie_t async_schedule(async_func_ptr *ptr, void *data);
>>  extern async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data,
>>  					    struct list_head *list);
>> +extern async_cookie_t async_schedule_atomic(async_func_ptr *ptr, void *data);
>> +extern async_cookie_t async_schedule_domain_atomic(async_func_ptr *ptr, \
>
>
>trailing backslash?
>
>
>> +					void *data, struct list_head *list);
>>  extern void async_synchronize_full(void);
>>  extern void async_synchronize_full_domain(struct list_head *list);
>>  extern void async_synchronize_cookie(async_cookie_t cookie);
>> diff --git a/kernel/async.c b/kernel/async.c
>> index 968ef94..6bf565b 100644
>> --- a/kernel/async.c
>> +++ b/kernel/async.c
>> @@ -172,12 +172,13 @@ out:
>>  }
>>  
>>  
>> -static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
>> +static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, \
>
>
>another one.
>
>
>> +				struct list_head *running, int atomic)
>>  {
>>  	struct async_entry *entry;
>>  	unsigned long flags;
>>  	async_cookie_t newcookie;
>> -	
>> +	int  sync_run = 0;
>>  
>>  	/* allow irq-off callers */
>>  	entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
>> @@ -186,7 +187,9 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
>>  	 * If we're out of memory or if there's too much work
>>  	 * pending already, we execute synchronously.
>>  	 */
>> -	if (!async_enabled || !entry || atomic_read(&entry_count) > MAX_WORK) {
>> +	sync_run = !async_enabled || !entry || \
>> +			atomic_read(&entry_count) > MAX_WORK;


And also this one...

Hey, Ming, none of these are macros... You don't need to add backslash to
join two lines, C compilers can recognize.

-- 
Live like a child, think like the god.
 
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