Re: [PATCH RFC tip/core/rcu 31/41] rcu: Add CPU-stall capability torcutorture

From: Julia Lawall
Date: Thu Feb 02 2012 - 04:15:48 EST

On Wed, 1 Feb 2012, Josh Triplett wrote:

On Wed, Feb 01, 2012 at 11:41:49AM -0800, Paul E. McKenney wrote:
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
+/* Spawn CPU-stall kthread, if stall_cpu specified. */
+static int __init rcu_torture_stall_init(void)
+ if (stall_cpu <= 0)
+ return 0;
+ stall_task = kthread_run(rcu_torture_stall, NULL, "rcu_torture_stall");
+ if (IS_ERR(stall_task)) {
+ stall_task = NULL;
+ return PTR_ERR(stall_task);

This seems...unlikely to produce the desired result. :)

A quick check turns up the same bug in rcutorture_onoff_init.

This suggests a possible Coccinelle check, for uses of PTR_ERR(foo) after
foo = (any constant other than ERR_PTR(foo)).

Indeed, it seems to be a popular idiom :) I'll send some patches later today.

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