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Subject[tip: sched/core] sched/nohz: Remove unnecessarily complex error handling pattern from find_new_ilb()
The following commit has been merged into the sched/core branch of tip:

Commit-ID: f4bb5705114530cd775a5a649b666755b3efe7aa
Gitweb: https://git.kernel.org/tip/f4bb5705114530cd775a5a649b666755b3efe7aa
Author: Ingo Molnar <mingo@kernel.org>
AuthorDate: Fri, 06 Oct 2023 12:25:18 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 09 Oct 2023 12:21:23 +02:00

sched/nohz: Remove unnecessarily complex error handling pattern from find_new_ilb()

find_new_ilb() returns nr_cpu_ids on failure - which is the usual
cpumask bitops return pattern, but is weird & unnecessary in this
context: not only is it a global variable, it it is a +1 out of
bounds CPU index and also has different signedness ...

Its only user, kick_ilb(), then checks the return against nr_cpu_ids
to decide to return. There's no other use.

So instead of this, use a standard -1 return on failure to find an
idle CPU, as the argument is signed already.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/r/20231006102518.2452758-4-mingo@kernel.org
---
kernel/sched/fair.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f82b301..19bb4ac 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11528,7 +11528,7 @@ static inline int find_new_ilb(void)
return ilb_cpu;
}

- return nr_cpu_ids;
+ return -1;
}

/*
@@ -11549,8 +11549,7 @@ static void kick_ilb(unsigned int flags)
nohz.next_balance = jiffies+1;

ilb_cpu = find_new_ilb();
-
- if (ilb_cpu >= nr_cpu_ids)
+ if (ilb_cpu < 0)
return;

/*
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