On 12/14/2011 08:43 PM, Josh Triplett wrote:
> On Wed, Dec 14, 2011 at 08:34:26PM +0100, Lars-Peter Clausen wrote:
>> On 12/14/2011 08:29 PM, Lars-Peter Clausen wrote:
>>> On 12/14/2011 08:08 PM, Josh Triplett wrote:
>>>> In the Linux kernel, "current" refers to the current task, of type
>>>> "struct task_struct *", by way of a stack of (sometimes arch-specific)
>>>> macros. For instance, arch/x86/include/asm/current.h defines current as
>>>> get_current(), an inline function returning "struct task_struct *".
>>>> Other architectures, as well as asm-generic, use variations on the same
>>>> theme with varying depths of macros.
>>>>
>>>> However, coccinelle doesn't seem to manage to figure out the type of
>>>> current, because rules defined with @@struct task_struct *task;@@ don't
>>>> match current.
>>>>
>>>> I can work around this by writing a duplicate set of rules with
>>>> @@identifier current;@@, but I'd rather not have to introduce that
>>>> duplication.
>>>>
>>>> For a test case, try the following semantic patch:
>>>>
>>>> @@ struct task_struct *task; @@
>>>> - (task)->pid == 0
>>>> + is_idle_task(task)
>>>>
>>>> @@ struct task_struct *task; @@
>>>> - (task)->pid != 0
>>>> + !is_idle_task(task)
>>>>
>>>>
>>>> And the following test file:
>>>>
>>>> #include <linux/sched.h>
>>>> extern struct task_struct *t;
>>>> void context(void)
>>>> {
>>>> if (t->pid)
>>>> do_something();
>>>> if (current->pid)
>>>> do_something();
>>>> }
>>>>
>>>>
>>>> Coccinelle successfully patches the first condition, but not the second.
>>>
>>> Did you ran spatch with -all_includes?
>>
>> Sorry, make that -recursive_includes.
>
> Good to know. "make coccicheck" in the Linux kernel doesn't currently
> use either of those two options; should it?
You don't want to use that for all the scripts as it can have a
significant performance impact. E.g. for some of my scripts running on
Wine code it can make the difference between "finishes in 30 seconds"
and "killed it after it burned more than 2 hours CPU time".
bye
michael
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