static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
					 struct task_struct *next)
{
	struct perf_event_context *ctx = task->perf_event_ctxp[ctxn];
	struct perf_event_context *next_ctx;
	struct perf_event_context *parent, *next_parent;
	struct perf_cpu_context *cpuctx;
	int do_switch = 1;

	if (likely(!ctx))
		return;

	cpuctx = __get_cpu_context(ctx);
	if (!cpuctx->task_ctx)
		return;

	rcu_read_lock();
	next_ctx = next->perf_event_ctxp[ctxn];
	if (!next_ctx)
		goto unlock;

	parent = rcu_dereference(ctx->parent_ctx);
	next_parent = rcu_dereference(next_ctx->parent_ctx);

	/* If neither context have a parent context; they cannot be clones. */
	if (!parent && !next_parent)
		goto unlock;

	if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
		/*
		 * Looks like the two contexts are clones, so we might be
		 * able to optimize the context switch.  We lock both
		 * contexts and check that they are clones under the
		 * lock (including re-checking that neither has been
		 * uncloned in the meantime).  It doesn't matter which
		 * order we take the locks because no other cpu could
		 * be trying to lock both of these tasks.
		 */
		raw_spin_lock(&ctx->lock);
		raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
		if (context_equiv(ctx, next_ctx)) {
			WRITE_ONCE(ctx->task, next);
			WRITE_ONCE(next_ctx->task, task);

			swap(ctx->task_ctx_data, next_ctx->task_ctx_data);

			/*
			 * RCU_INIT_POINTER here is safe because we've not
			 * modified the ctx and the above modification of
			 * ctx->task and ctx->task_ctx_data are immaterial
			 * since those values are always verified under
			 * ctx->lock which we're now holding.
			 */
			RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], next_ctx);
			RCU_INIT_POINTER(next->perf_event_ctxp[ctxn], ctx);

			do_switch = 0;

			perf_event_sync_stat(ctx, next_ctx);
		}
		raw_spin_unlock(&next_ctx->lock);
		raw_spin_unlock(&ctx->lock);
	}
unlock:
	rcu_read_unlock();

	if (do_switch) {
		raw_spin_lock(&ctx->lock);
		task_ctx_sched_out(cpuctx, ctx, EVENT_ALL);
		raw_spin_unlock(&ctx->lock);
	}
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.