From: NeilBrown <neilb@suse.com>
Date: Sat, 12 May 2018 17:52:58 +0000 (-0400)
Subject: LU-4423 libcfs: disable preempt while sampling processor id.
X-Git-Tag: 2.11.53~87
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=32c7b181371c75c5a5e79c603972be09c3deb2d4;ds=sidebyside

LU-4423 libcfs: disable preempt while sampling processor id.

Calling smp_processor_id() without disabling preemption
triggers a warning (if CONFIG_DEBUG_PREEMPT).
I think the result of cfs_cpt_current() is only used as a hint for
load balancing, rather than as a precise and stable indicator of
the current CPU.  So it doesn't need to be called with
preemption disabled.

So disable preemption inside cfs_cpt_current() to silence the warning.

Linux-commit : dbeccabf5294e80f7cc9ee566746c42211bed736

Change-Id: Iaa930acc7a2633c0e40bcabbe6bd309a3d767325
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/32360
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---

diff --git a/libcfs/libcfs/libcfs_cpu.c b/libcfs/libcfs/libcfs_cpu.c
index 18c4839..c80f9d4 100644
--- a/libcfs/libcfs/libcfs_cpu.c
+++ b/libcfs/libcfs/libcfs_cpu.c
@@ -678,19 +678,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node);
 
 int cfs_cpt_current(struct cfs_cpt_table *cptab, int remap)
 {
-	int cpu = smp_processor_id();
-	int cpt = cptab->ctb_cpu2cpt[cpu];
+	int cpu;
+	int cpt;
 
-	if (cpt < 0) {
-		if (!remap)
-			return cpt;
+	preempt_disable();
+	cpu = smp_processor_id();
+	cpt = cptab->ctb_cpu2cpt[cpu];
 
+	if (cpt < 0 && remap) {
 		/* don't return negative value for safety of upper layer,
 		 * instead we shadow the unknown cpu to a valid partition ID
 		 */
 		cpt = cpu % cptab->ctb_nparts;
 	}
-
+	preempt_enable();
 	return cpt;
 }
 EXPORT_SYMBOL(cfs_cpt_current);