Messages in this thread | | | Date | Sat, 06 Jul 2013 13:36:27 +0530 | From | Preeti U Murthy <> | Subject | Re: [PATCH 3/3] smp/ipi:Remove check around csd lock in handler for smp_call_function variants |
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On 07/06/2013 11:15 AM, Wang YanQing wrote: > 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 :)
Sorry about this error :) > >> Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> >> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> >> Cc: Ingo Molnar <mingo@elte.hu> >> Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> >> Cc: srivatsa.bhat@linux.vnet.ibm.com >> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> >> Cc: Steven Rostedt <rostedt@goodmis.org> >> Cc: Rusty Russell <rusty@rustcorp.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.
Right, I will include it in the changelog.
> 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.
Ideally it should be under a WARN_ON(). csd_unlock() has that WARN_ON(). Unlocking a parameter which is not locked should be seen as a bug, which the above code is not doing. In fact it avoids it being reported as a bug.
> > Just like you can't know who and how people will use the > API, so some robust check code is good. >
Regards Preeti U Murthy
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