[PATCH v3] sched/isolation: add a workqueue parameter onto isolcpus to constrain unbound CPUs

[tiozhang <tiozhang@didiglobal.com>]

Motivation of doing this is to better improve boot times for devices when
we want to prevent our workqueue works from running on some specific CPUs,
i,e, some CPUs are busy with interrupts.

Also remove HK_FLAG_WQ from nohz_full to prevent nohz_full overriding
workqueue's cpu config.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: tiozhang <tiozhang@didiglobal.com>
---
 kernel/sched/isolation.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 373d42c707bc..5cd67c51622e 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -181,8 +181,8 @@ static int __init housekeeping_nohz_full_setup(char *str)
 {
 	unsigned long flags;
 
-	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
-		HK_FLAG_MISC | HK_FLAG_KTHREAD;
+	flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC
+		| HK_FLAG_KTHREAD;
 
 	return housekeeping_setup(str, flags);
 }
@@ -208,6 +208,12 @@ static int __init housekeeping_isolcpus_setup(char *str)
 			continue;
 		}
 
+		if (!strncmp(str, "workqueue,", 10)) {
+			str += 10;
+			flags |= HK_FLAG_WQ;
+			continue;
+		}
+
 		if (!strncmp(str, "managed_irq,", 12)) {
 			str += 12;
 			flags |= HK_FLAG_MANAGED_IRQ;
-- 
2.17.1