tick/nohz: Fix inverted return value in check_tick_dependency() fast path

Commit 56534673cea7f ("tick/nohz: Optimize check_tick_dependency() with
early return") added a fast path that returns !val when the tick_stop
tracepoint is disabled.

This is inverted: the slow path returns true when a dependency IS found
(val != 0), but !val returns true when val is zero (no dependency).  The
result is that can_stop_full_tick() sees "dependency found" when there are
none, and the tick never stops on nohz_full CPUs.

Fix this by returning !!val instead of !val, matching the slow-path semantics.

Fixes: 56534673cea7f ("tick/nohz: Optimize check_tick_dependency() with early return")
Signed-off-by: Josh Snyder <josh@code406.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Link: https://patch.msgid.link/20260402-fix-idle-tick2-v1-1-eecb589649d3@code406.com

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f7907fadd63f211e1aef531db239e1a4cd140361..36449f0010a452b413920b70f8dec24b3cb8f187 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -345,7 +345,7 @@ static bool check_tick_dependency(atomic_t *dep)
        int val = atomic_read(dep);
 
        if (likely(!tracepoint_enabled(tick_stop)))
-               return !val;
+               return !!val;
 
        if (val & TICK_DEP_MASK_POSIX_TIMER) {
                trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);