[PATCH] smp: Remove CSD_FLAG_WAIT flag that's unused

[PATCH] smp: Remove CSD_FLAG_WAIT flag that's unused

[Tim Chen]

The CSD_FLAG_WAIT is not serving any useful purpose as we do not use
its value to decide if we are going to wait for a smp call to complete.
We also never cleared it properly when we are done waiting to indicate
that the wait is over.  So the WARNING debug check in csd_unlock is
also not serving useful purpose.  Propose here to remove it to clean up
the code.

Thanks.

Tim

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
 kernel/smp.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index f38a1e6..b65420d 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -19,7 +19,6 @@
 
 enum {
 	CSD_FLAG_LOCK		= 0x01,
-	CSD_FLAG_WAIT		= 0x02,
 };
 
 struct call_function_data {
@@ -126,7 +125,7 @@ static void csd_lock(struct call_single_data *csd)
 
 static void csd_unlock(struct call_single_data *csd)
 {
-	WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
+	WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
 
 	/*
 	 * ensure we're all done before releasing data:
@@ -173,9 +172,6 @@ static int generic_exec_single(int cpu, struct call_single_data *csd,
 	csd->func = func;
 	csd->info = info;
 
-	if (wait)
-		csd->flags |= CSD_FLAG_WAIT;
-
 	/*
 	 * The list addition should be visible before sending the IPI
 	 * handler locks the list to pull the entry off it because of
-- 
1.9.3

Re: [PATCH] smp: Remove CSD_FLAG_WAIT flag that's unused

[Peter Zijlstra]

On Fri, Feb 27, 2015 at 12:36:13PM -0800, Tim Chen wrote:
> 
> The CSD_FLAG_WAIT is not serving any useful purpose as we do not use
> its value to decide if we are going to wait for a smp call to complete.
> We also never cleared it properly when we are done waiting to indicate
> that the wait is over.  So the WARNING debug check in csd_unlock is
> also not serving useful purpose.  Propose here to remove it to clean up
> the code.

Linus had a much more comprehensive patch:

  http://marc.info/?l=linux-kernel&m=142368734118230