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Subject: Re: posix-cpu-timers revamp
From: Frank Mayhar <fmayhar@google.com>
To: Roland McGrath <roland@redhat.com>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <20080402020707.151E126F8DC@magilla.localdomain>
References: <bug-9906-10286@http.bugzilla.kernel.org/>
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Content-Type: text/plain
Organization: Google, Inc.
Date: Wed, 02 Apr 2008 11:42:40 -0700
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On Tue, 2008-04-01 at 19:07 -0700, Roland McGrath wrote:
> > To deal with the need for bookkeeping with multiple threads in the SMP
> > case (where there isn't a per-cpu structure until it's needed), I'll
> > allocate the per-cpu structure in __exit_signal() where the relevant
> > fields are updated.  I'll also allocate it where I do now, in
> > do_setitimer(), when needed.  The allocation will be a "return 0" for UP
> > and a call to "thread_group_times_alloc_smp()" (which lives in sched.c)
> > for SMP.
> 
> By do_setitimer, you mean set_process_cpu_timer and posix_cpu_timer_set.

And another quick note:  It appears that with the "allocate percpu
storage in copy_signal CLONE_THREAD case" mechanism, I don't need to
worry about allocating it anywhere else.  If I need it (which is only in
the case of multiple threads and an interval timer) then I'll have it
because it was allocated with the second thread.  So I just eliminate
the allocation in do_setitimer() entirely.
-- 
Frank Mayhar <fmayhar@google.com>
Google, Inc.