On Sat, 11 Jan 2014 10:28:51 +0900 Tetsuo Handa
<penguin-ker...@i-love.sakura.ne.jp> wrote:
> Andrew Morton wrote:
> > On Thu, 9 Jan 2014 21:52:00 +0900 Tetsuo Handa
> > <penguin-ker...@i-love.sakura.ne.jp> wrote:
> >
> > > This patch introduces %pT format specifier for printing task_struct->comm.
> > > Currently %pT does not provide consistency. I'm planning to change to use
> > > RCU
> > > in the future. By using RCU, the comm name read from task_struct->comm
> > > will be
> > > guaranteed to be consistent. But before modifying set_task_comm() to use
> > > RCU,
> > > we need to kill direct ->comm users who do not use get_task_comm().
> >
> > On reflection...
> >
> > It isn't obvious that this patch is sufficiently beneficial until we
> > have that RCU code in place.
> >
> > So I could retain this patch in -mm until we have that all sorted out.
> > And I'll have to avoid merging %pT users into mainline in the
> > meanwhile!
> >
> > Am I wrong? The patch seems fairly pointless as a standalone thing?
> >
>
> Step 1: (targeted to 3.14-rc1)
> Add "%pT" format specifier and commcpy() wrapper function.
>
> Step 2: (started after step 1 is reflected to other git trees)
> Replace printk("%s", p->comm) with printk("%pT", p).
> Replace strcpy(buf, p->comm) with commcpy(buf, p).
>
> Step 3: (started after step 2 is reflected to other git trees)
> Add rcu_read_lock()/rcu_read_unlock() into commcpy().
> Modify set_task_comm() etc. to replace ->comm using RCU.
In the absence of step 3, steps 1 and 2 are rather pointless churn.
So I think it would be better to merge (into mainline) steps 1 and 3
first and at the same time. Then start thinking about step 2.
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