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authorOleg Nesterov <oleg@redhat.com>2024-04-13 16:17:46 +0200
committerIngo Molnar <mingo@kernel.org>2024-04-28 10:08:21 +0200
commit257bf89d84121280904800acd25cc2c444c717ae (patch)
tree77885bdc1eb9b3d3d7bd1b93de4c9fad7954102a /kernel/sched/isolation.c
parentsched/isolation: Prevent boot crash when the boot CPU is nohz_full (diff)
downloadlinux-257bf89d84121280904800acd25cc2c444c717ae.tar.xz
linux-257bf89d84121280904800acd25cc2c444c717ae.zip
sched/isolation: Fix boot crash when maxcpus < first housekeeping CPU
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
Diffstat (limited to 'kernel/sched/isolation.c')
-rw-r--r--kernel/sched/isolation.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 2a262d3ecb3d..5891e715f00d 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -118,6 +118,7 @@ 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)) {
@@ -138,7 +139,8 @@ 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) {
@@ -147,6 +149,9 @@ 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;