rcu: Fix RCU CPU stall detection in tiny implementation (ec1fe396) · Commits · 戴 / test

The tiny RCU CPU stall detection depends on *rcp->curtail not being NULL. It is however a tail pointer and thus NULL by definition. Instead we should check rcp->rcucblist for the presence of pending callbacks which need to be processed. With this fix INFO about the stall is printed and jiffies_stall (jiffies at next stall) correctly updated. Note that the check for pending callback is necessary to avoid spurious warnings if there are no pendings callbacks. Signed-off-by:

Miroslav Benes <mbenes@suse.cz> [ paulmck: Fused identical "if" statements, ported to -rcu. ] Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tiny_plugin.h

+3 −4

Original line number	Diff line number	Diff line
		@@ -145,18 +145,17 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
		rcp->ticks_this_gp++;
		j = jiffies;
		js = ACCESS_ONCE(rcp->jiffies_stall);
		if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
		if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {
		pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
		rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
		jiffies - rcp->gp_start, rcp->qlen);
		dump_stack();
		}
		if (*rcp->curtail && ULONG_CMP_GE(j, js))
		ACCESS_ONCE(rcp->jiffies_stall) = jiffies +
		3 * rcu_jiffies_till_stall_check() + 3;
		else if (ULONG_CMP_GE(j, js))
		} else if (ULONG_CMP_GE(j, js)) {
		ACCESS_ONCE(rcp->jiffies_stall) = jiffies + rcu_jiffies_till_stall_check();
		}
		}

		static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
		{

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