mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-27 21:03:32 +00:00
sched/isolation: Fix boot crash when maxcpus < first housekeeping CPU
[ Upstream commit 257bf89d84
]
housekeeping_setup() checks cpumask_intersects(present, online) to ensure
that the kernel will have at least one housekeeping CPU after smp_init(),
but this doesn't work if the maxcpus= kernel parameter limits the number of
processors available after bootup.
For example, a kernel with "maxcpus=2 nohz_full=0-2" parameters crashes at
boot time on a virtual machine with 4 CPUs.
Change housekeeping_setup() to use cpumask_first_and() and check that the
returned CPU number is valid and less than setup_max_cpus.
Another corner case is "nohz_full=0" on a machine with a single CPU or with
the maxcpus=1 kernel argument. In this case non_housekeeping_mask is empty
and tick_nohz_full_setup() makes no sense. And indeed, the kernel hits the
WARN_ON(tick_nohz_full_running) in tick_sched_do_timer().
And how should the kernel interpret the "nohz_full=" parameter? It should
be silently ignored, but currently cpulist_parse() happily returns the
empty cpumask and this leads to the same problem.
Change housekeeping_setup() to check cpumask_empty(non_housekeeping_mask)
and do nothing in this case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240413141746.GA10008@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
e477e2e426
commit
e3decad6ab
1 changed files with 6 additions and 1 deletions
|
@ -109,6 +109,7 @@ static void __init housekeeping_setup_type(enum hk_type type,
|
|||
static int __init housekeeping_setup(char *str, unsigned long flags)
|
||||
{
|
||||
cpumask_var_t non_housekeeping_mask, housekeeping_staging;
|
||||
unsigned int first_cpu;
|
||||
int err = 0;
|
||||
|
||||
if ((flags & HK_FLAG_TICK) && !(housekeeping.flags & HK_FLAG_TICK)) {
|
||||
|
@ -129,7 +130,8 @@ static int __init housekeeping_setup(char *str, unsigned long flags)
|
|||
cpumask_andnot(housekeeping_staging,
|
||||
cpu_possible_mask, non_housekeeping_mask);
|
||||
|
||||
if (!cpumask_intersects(cpu_present_mask, housekeeping_staging)) {
|
||||
first_cpu = cpumask_first_and(cpu_present_mask, housekeeping_staging);
|
||||
if (first_cpu >= nr_cpu_ids || first_cpu >= setup_max_cpus) {
|
||||
__cpumask_set_cpu(smp_processor_id(), housekeeping_staging);
|
||||
__cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
|
||||
if (!housekeeping.flags) {
|
||||
|
@ -138,6 +140,9 @@ static int __init housekeeping_setup(char *str, unsigned long flags)
|
|||
}
|
||||
}
|
||||
|
||||
if (cpumask_empty(non_housekeeping_mask))
|
||||
goto free_housekeeping_staging;
|
||||
|
||||
if (!housekeeping.flags) {
|
||||
/* First setup call ("nohz_full=" or "isolcpus=") */
|
||||
enum hk_type type;
|
||||
|
|
Loading…
Reference in a new issue