[PATCH AUTOSEL for 4.15 067/124] staging: lustre: disable preempt while sampling processor id.

Sasha Levin
2018-03-19T15:48:59Z

From: NeilBrown <neilb@suse.com>

[ Upstream commit dbeccabf5294e80f7cc9ee566746c42211bed736 ]

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.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
index 51823ce71773..a013f7eb208f 100644
--- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
+++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
@@ -529,19 +529,20 @@ 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);
--
2.14.1