Re: [SYSTEMTAP/PATCH 0/4] RT aware systemtap patch set

[Santosh Shukla <sshukla@mvista.com>]

On Mon, Sep 15, 2014 at 10:15 PM, Josh Stone <jistone@redhat.com> wrote:
> On 09/15/2014 09:35 AM, Santosh Shukla wrote:
>> On Mon, Sep 15, 2014 at 9:52 PM, Josh Stone <jistone@redhat.com> wrote:
>>> Hi,
>>>
>>> On 09/15/2014 08:41 AM, Santosh Shukla wrote:
>>>> first wanted to get raw_locking specific to get into stap.
>>>
>>> One ugly aspect of this is that we try to maintain compatibility with
>>> older platforms too.  It looks like raw_spin_lock didn't come into the
>>> kernel until 2.6.33, which doesn't even cover RHEL6.  If possible we try
>>> to keep things running all the way back to RHEL4 (though see my earlier
>>> RFC about dropping that).
>>
>> Right, I did saw your early RFC and noticed few important stuff
>> missing so to keep compatibility per se  .i..e.. some type of locking
>> function helper api which could ably switch between PREEMPT and
>> non-PREEMPT kernel.
>>
>>
>> In v2 version which I am working on [inspired by Corey suggestion] to
>> add below type of locking facility, pseudo code look like below
>>
>> #ifdef CONFIG_PREEMPT_RT
>> static inline my_readlock(raw_spinlock_t *lock) { raw_spin_lock(&lock); }
>> static inline my_readunlock(raw_spinlock_t *lock) {
>> raw_spin_unlock(&lock); }
>> static inline my_writelock(raw_spinlock_t *lock) { raw_spin_lock(&lock); }
>> static inline my_writeunlock(raw_spinlock_t *lock) {
>> raw_spin_unlock(&lock); }
>> #else
>> static inline my_readlock(rwlock_t *lock) {read_lock(&lock); }
>> static inline my_readunlock(rwlock_t *lock) {read_unlock(&lock); }
>> static inline my_writelock(rwlock_t *lock) { write_lock(&lock); }
>> static inline my_writeunlock(rwlock_t *lock) {write_unlock(&lock); }
>> #endif
>
> Ok, if the raw interfaces have always existed with PREEMPT_RT, then this
> should be fine.
>
Yes they are.

> I suggest "stp_" rather than "my_" though.  </bikeshed>

Yup.