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Date: Sat, 6 Jul 2013 13:45:53 +0800 From: Wang YanQing <udknight@...il.com> To: Preeti U Murthy <preeti@...ux.vnet.ibm.com> Cc: xiaoguangrong@...fujitsu.com, mingo@...e.hu, paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl, npiggin@...e.de, deepthi@...ux.vnet.ibm.com, peterz@...radead.org, rusty@...tcorp.com.au, heiko.carstens@...ibm.com, rostedt@...dmis.org, miltonm@....com, srivatsa.bhat@...ux.vnet.ibm.com, jens.axboe@...cle.com, tj@...nel.org, akpm@...ux-foundation.org, svaidy@...ux.vnet.ibm.com, shli@...nel.org, tglx@...utronix.de, lig.fnst@...fujitsu.com, anton@...ba.org Subject: Re: [PATCH 3/3] smp/ipi:Remove check around csd lock in handler for smp_call_function variants On Fri, Jul 05, 2013 at 09:57:21PM +0530, Preeti U Murthy wrote: > call_single_data is always locked by all callers of > arch_send_call_function_single_ipi() or > arch_send_call_function_ipi_mask() which results in execution of > generic_call_function_interrupt() handler. > > Hence remove the check for lock on csd in generic_call_function_interrupt() > handler, before unlocking it. I can't find where is the generic_call_function_interrupt :) > Signed-off-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl> > Cc: Ingo Molnar <mingo@...e.hu> > Cc: Xiao Guangrong <xiaoguangrong@...fujitsu.com> > Cc: srivatsa.bhat@...ux.vnet.ibm.com > Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> > Cc: Steven Rostedt <rostedt@...dmis.org> > Cc: Rusty Russell <rusty@...tcorp.com.au > --- > > kernel/smp.c | 14 +------------- > 1 file changed, 1 insertion(+), 13 deletions(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index b6981ae..d37581a 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -181,25 +181,13 @@ void generic_smp_call_function_single_interrupt(void) > > while (!list_empty(&list)) { > struct call_single_data *csd; > - unsigned int csd_flags; > > csd = list_entry(list.next, struct call_single_data, list); > list_del(&csd->list); > > - /* > - * 'csd' can be invalid after this call if flags == 0 > - * (when called through generic_exec_single()), > - * so save them away before making the call: > - */ > - csd_flags = csd->flags; > - You haven't mention this change in the ChangeLog, don't do it. I can't see any harm to remove csd_flags, but I hope others check it again. > csd->func(csd->info); > > - /* > - * Unlocked CSDs are valid through generic_exec_single(): > - */ > - if (csd_flags & CSD_FLAG_LOCK) > - csd_unlock(csd); > + csd_unlock(csd); I don't like this change, I think check CSD_FLAG_LOCK to make sure we really need csd_unlock is good. Just like you can't know who and how people will use the API, so some robust check code is good. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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