linux-kernel - Re: [RFC PATCH v2 15/25] smp, ppc: kill SMP single function call interrupt

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Message-ID: <5231C9F3.4060208@gmail.com>
Date:	Thu, 12 Sep 2013 22:04:35 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Shaohua Li <shli@...nel.org>, linux-arch@...r.kernel.org,
	Jiri Kosina <trivial@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Wang YanQing <udknight@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	linuxppc-dev@...ts.ozlabs.org, Jiang Liu <jiang.liu@...wei.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH v2 15/25] smp, ppc: kill SMP single function call
 interrupt

On 09/12/2013 04:03 AM, Srivatsa S. Bhat wrote:
> On 09/11/2013 09:37 PM, Jiang Liu wrote:
>> From: Jiang Liu <jiang.liu@...wei.com>
>>
>> Commit 9a46ad6d6df3b54 "smp: make smp_call_function_many() use logic
>> similar to smp_call_function_single()" has unified the way to handle
>> single and multiple cross-CPU function calls. Now only one interrupt
>> is needed for architecture specific code to support generic SMP function
>> call interfaces, so kill the redundant single function call interrupt.
>>
>> Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
>> Cc: Jiang Liu <liuj97@...il.com>
>> ---
> 
> It turns out that freeing up the IPI slot in powerpc is very useful, since
> we actually wanted a slot for some other use-case (and there are only 4 slots
> available on powerpc).
> 
> Here are the patches which achieve that:
> http://marc.info/?l=linuxppc-embedded&m=137886807502898&w=2
> http://marc.info/?l=linuxppc-embedded&m=137886811502909&w=2
Hi Srivatsa,
	That's great and I will drop this patch from my series.
Could you please to kill call_function_single_action() instead of
call_function_action()? Please refer to
http://lkml.org/lkml/2013/9/11/579
Regards!
Gerry

> 
> So, can you kindly consider dropping the powerpc patch from your series,
> if that is OK with you? Thanks!
> 
> BTW, after doing the powerpc cleanup, even I had thought about killing one
> of the smp-function variants in various architectures, but never got around
> to do it. But now that you have posted the series which does that, I'll try
> to review them.
> 
> Thank you!
> 
> Regards,
> Srivatsa S. Bhat
> 
>>  arch/powerpc/include/asm/smp.h |  3 +--
>>  arch/powerpc/kernel/smp.c      | 12 +-----------
>>  2 files changed, 2 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
>> index 48cfc85..53faa03 100644
>> --- a/arch/powerpc/include/asm/smp.h
>> +++ b/arch/powerpc/include/asm/smp.h
>> @@ -119,8 +119,7 @@ extern int cpu_to_core_id(int cpu);
>>   * in /proc/interrupts will be wrong!!! --Troy */
>>  #define PPC_MSG_CALL_FUNCTION   0
>>  #define PPC_MSG_RESCHEDULE      1
>> -#define PPC_MSG_CALL_FUNC_SINGLE	2
>> -#define PPC_MSG_DEBUGGER_BREAK  3
>> +#define PPC_MSG_DEBUGGER_BREAK  2
>>
>>  /* for irq controllers that have dedicated ipis per message (4) */
>>  extern int smp_request_message_ipi(int virq, int message);
>> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
>> index 38b0ba6..0c53b10 100644
>> --- a/arch/powerpc/kernel/smp.c
>> +++ b/arch/powerpc/kernel/smp.c
>> @@ -123,12 +123,6 @@ static irqreturn_t reschedule_action(int irq, void *data)
>>  	return IRQ_HANDLED;
>>  }
>>
>> -static irqreturn_t call_function_single_action(int irq, void *data)
>> -{
>> -	generic_smp_call_function_single_interrupt();
>> -	return IRQ_HANDLED;
>> -}
>> -
>>  static irqreturn_t debug_ipi_action(int irq, void *data)
>>  {
>>  	if (crash_ipi_function_ptr) {
>> @@ -146,14 +140,12 @@ static irqreturn_t debug_ipi_action(int irq, void *data)
>>  static irq_handler_t smp_ipi_action[] = {
>>  	[PPC_MSG_CALL_FUNCTION] =  call_function_action,
>>  	[PPC_MSG_RESCHEDULE] = reschedule_action,
>> -	[PPC_MSG_CALL_FUNC_SINGLE] = call_function_single_action,
>>  	[PPC_MSG_DEBUGGER_BREAK] = debug_ipi_action,
>>  };
>>
>>  const char *smp_ipi_name[] = {
>>  	[PPC_MSG_CALL_FUNCTION] =  "ipi call function",
>>  	[PPC_MSG_RESCHEDULE] = "ipi reschedule",
>> -	[PPC_MSG_CALL_FUNC_SINGLE] = "ipi call function single",
>>  	[PPC_MSG_DEBUGGER_BREAK] = "ipi debugger",
>>  };
>>
>> @@ -225,8 +217,6 @@ irqreturn_t smp_ipi_demux(void)
>>  			generic_smp_call_function_interrupt();
>>  		if (all & (1 << (24 - 8 * PPC_MSG_RESCHEDULE)))
>>  			scheduler_ipi();
>> -		if (all & (1 << (24 - 8 * PPC_MSG_CALL_FUNC_SINGLE)))
>> -			generic_smp_call_function_single_interrupt();
>>  		if (all & (1 << (24 - 8 * PPC_MSG_DEBUGGER_BREAK)))
>>  			debug_ipi_action(0, NULL);
>>  #else
>> @@ -257,7 +247,7 @@ EXPORT_SYMBOL_GPL(smp_send_reschedule);
>>
>>  void arch_send_call_function_single_ipi(int cpu)
>>  {
>> -	do_message_pass(cpu, PPC_MSG_CALL_FUNC_SINGLE);
>> +	do_message_pass(cpu, PPC_MSG_CALL_FUNCTION);
>>  }
>>
>>  void arch_send_call_function_ipi_mask(const struct cpumask *mask)
>>
> 

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