[PATCH 2/4 v2] cgroup: rstat lock indirection

[inwardvessel <inwardvessel@xxxxxxxxx>]

From: JP Kobryn <inwardvessel@xxxxxxxxx>

Instead of accessing the target lock directly via global var, access it
indirectly in the form of a new parameter. Also change the ordering of
the parameters to be consistent with the related per-cpu locking
function _cgroup_rstat_cpu_lock().

Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Signed-off-by: JP Kobryn <inwardvessel@xxxxxxxxx>
---
 kernel/cgroup/rstat.c | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 9976f9acd62b..88908ef9212d 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -277,7 +277,7 @@ __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
 __bpf_hook_end();
 
 /*
- * Helper functions for locking cgroup_rstat_lock.
+ * Helper functions for locking.
  *
  * This makes it easier to diagnose locking issues and contention in
  * production environments.  The parameter @cpu_in_loop indicate lock
@@ -285,29 +285,32 @@ __bpf_hook_end();
  * value -1 is used when obtaining the main lock else this is the CPU
  * number processed last.
  */
-static inline void __cgroup_rstat_lock(struct cgroup *cgrp, int cpu_in_loop)
-	__acquires(&cgroup_rstat_lock)
+static inline void __cgroup_rstat_lock(spinlock_t *lock,
+		struct cgroup *cgrp, int cpu_in_loop)
+	__acquires(lock)
 {
 	bool contended;
 
-	contended = !spin_trylock_irq(&cgroup_rstat_lock);
+	contended = !spin_trylock_irq(lock);
 	if (contended) {
 		trace_cgroup_rstat_lock_contended(cgrp, cpu_in_loop, contended);
-		spin_lock_irq(&cgroup_rstat_lock);
+		spin_lock_irq(lock);
 	}
 	trace_cgroup_rstat_locked(cgrp, cpu_in_loop, contended);
 }
 
-static inline void __cgroup_rstat_unlock(struct cgroup *cgrp, int cpu_in_loop)
-	__releases(&cgroup_rstat_lock)
+static inline void __cgroup_rstat_unlock(spinlock_t *lock,
+		struct cgroup *cgrp, int cpu_in_loop)
+	__releases(lock)
 {
 	trace_cgroup_rstat_unlock(cgrp, cpu_in_loop, false);
-	spin_unlock_irq(&cgroup_rstat_lock);
+	spin_unlock_irq(lock);
 }
 
 /* see cgroup_rstat_flush() */
-static void cgroup_rstat_flush_locked(struct cgroup_subsys_state *css)
-	__releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
+static void cgroup_rstat_flush_locked(struct cgroup_subsys_state *css,
+		spinlock_t *lock)
+	__releases(lock) __acquires(lock)
 {
 	struct cgroup *cgrp = css->cgroup;
 	int cpu;
@@ -328,11 +331,11 @@ static void cgroup_rstat_flush_locked(struct cgroup_subsys_state *css)
 		}
 
 		/* play nice and yield if necessary */
-		if (need_resched() || spin_needbreak(&cgroup_rstat_lock)) {
-			__cgroup_rstat_unlock(cgrp, cpu);
+		if (need_resched() || spin_needbreak(lock)) {
+			__cgroup_rstat_unlock(lock, cgrp, cpu);
 			if (!cond_resched())
 				cpu_relax();
-			__cgroup_rstat_lock(cgrp, cpu);
+			__cgroup_rstat_lock(lock, cgrp, cpu);
 		}
 	}
 }
@@ -356,9 +359,9 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup_subsys_state *css)
 
 	might_sleep();
 
-	__cgroup_rstat_lock(cgrp, -1);
-	cgroup_rstat_flush_locked(css);
-	__cgroup_rstat_unlock(cgrp, -1);
+	__cgroup_rstat_lock(&cgroup_rstat_lock, cgrp, -1);
+	cgroup_rstat_flush_locked(css, &cgroup_rstat_lock);
+	__cgroup_rstat_unlock(&cgroup_rstat_lock, cgrp, -1);
 }
 
 /**
@@ -375,8 +378,8 @@ void cgroup_rstat_flush_hold(struct cgroup_subsys_state *css)
 	struct cgroup *cgrp = css->cgroup;
 
 	might_sleep();
-	__cgroup_rstat_lock(cgrp, -1);
-	cgroup_rstat_flush_locked(css);
+	__cgroup_rstat_lock(&cgroup_rstat_lock, cgrp, -1);
+	cgroup_rstat_flush_locked(css, &cgroup_rstat_lock);
 }
 
 /**
@@ -386,7 +389,7 @@ void cgroup_rstat_flush_hold(struct cgroup_subsys_state *css)
 void cgroup_rstat_flush_release(struct cgroup_subsys_state *css)
 {
 	struct cgroup *cgrp = css->cgroup;
-	__cgroup_rstat_unlock(cgrp, -1);
+	__cgroup_rstat_unlock(&cgroup_rstat_lock, cgrp, -1);
 }
 
 int cgroup_rstat_init(struct cgroup_subsys_state *css)
-- 
2.43.5