[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <171429267151.10875.9512258624373740283.tip-bot2@tip-bot2>
Date: Sun, 28 Apr 2024 08:24:31 -0000
From: "tip-bot2 for Oleg Nesterov" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Oleg Nesterov <oleg@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, Phil Auld <pauld@...hat.com>,
Frederic Weisbecker <frederic@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: sched/urgent] sched/isolation: Fix boot crash when maxcpus <
first housekeeping CPU
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 257bf89d84121280904800acd25cc2c444c717ae
Gitweb: https://git.kernel.org/tip/257bf89d84121280904800acd25cc2c444c717ae
Author: Oleg Nesterov <oleg@...hat.com>
AuthorDate: Sat, 13 Apr 2024 16:17:46 +02:00
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Sun, 28 Apr 2024 10:08:21 +02:00
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@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Phil Auld <pauld@...hat.com>
Acked-by: Frederic Weisbecker <frederic@...nel.org>
Link: https://lore.kernel.org/r/20240413141746.GA10008@redhat.com
---
kernel/sched/isolation.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 2a262d3..5891e71 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;
Powered by blists - more mailing lists