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rcu: Report error for bad rcu_nocbs= parameter values

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This commit prints a console message when cpulist_parse() reports a
bad list of CPUs, and sets all CPUs' bits in that case.  The reason for
setting all CPUs' bits is that this is the safe(r) choice for real-time
workloads, which would normally be the ones using the rcu_nocbs= kernel
boot parameter.  Either way, later RCU console log messages list the
actual set of CPUs whose RCU callbacks will be offloaded.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney 2019-03-06 14:47:56 -08:00
parent da8739f23f
commit 497e42600b
1 changed files with 10 additions and 2 deletions
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12
kernel/rcu/tree_plugin.h
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@ -1772,14 +1772,22 @@ static void zero_cpu_stall_ticks(struct rcu_data *rdp)
*/
/* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */
/*
* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
* The string after the "rcu_nocbs=" is either "all" for all CPUs, or a
* comma-separated list of CPUs and/or CPU ranges. If an invalid list is
* given, a warning is emitted and all CPUs are offloaded.
*/
static int __init rcu_nocb_setup(char *str)
{
alloc_bootmem_cpumask_var(&rcu_nocb_mask);
if (!strcasecmp(str, "all"))
cpumask_setall(rcu_nocb_mask);
else
cpulist_parse(str, rcu_nocb_mask);
if (cpulist_parse(str, rcu_nocb_mask)) {
pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
cpumask_setall(rcu_nocb_mask);
}
return 1;
}
__setup("rcu_nocbs=", rcu_nocb_setup);