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| author | Valentin Schneider <valentin.schneider@arm.com> | 2021-05-18 16:07:25 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-06-28 16:42:24 +0300 |
| commit | 459b09b5a3254008b63382bf41a9b36d0b590f57 (patch) | |
| tree | 4b65f8808b64c12a3232275bf18aae6344e52a7c /kernel/sched/debug.c | |
| parent | 1c35b07e6d3986474e5635be566e7bc79d97c64d (diff) | |
| download | linux-459b09b5a3254008b63382bf41a9b36d0b590f57.tar.xz | |
sched/debug: Don't update sched_domain debug directories before sched_debug_init()
Since CPU capacity asymmetry can stem purely from maximum frequency
differences (e.g. Pixel 1), a rebuild of the scheduler topology can be
issued upon loading cpufreq, see:
arch_topology.c::init_cpu_capacity_callback()
Turns out that if this rebuild happens *before* sched_debug_init() is
run (which is a late initcall), we end up messing up the sched_domain debug
directory: passing a NULL parent to debugfs_create_dir() ends up creating
the directory at the debugfs root, which in this case creates
/sys/kernel/debug/domains (instead of /sys/kernel/debug/sched/domains).
This currently doesn't happen on asymmetric systems which use cpufreq-scpi
or cpufreq-dt drivers, as those are loaded via
deferred_probe_initcall() (it is also a late initcall, but appears to be
ordered *after* sched_debug_init()).
Ionela has been working on detecting maximum frequency asymmetry via ACPI,
and that actually happens via a *device* initcall, thus before
sched_debug_init(), and causes the aforementionned debugfs mayhem.
One option would be to punt sched_debug_init() down to
fs_initcall_sync(). Preventing update_sched_domain_debugfs() from running
before sched_debug_init() appears to be the safer option.
Fixes: 3b87f136f8fc ("sched,debug: Convert sysctl sched_domains to debugfs")
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lore.kernel.org/r/20210514095339.12979-1-ionela.voinescu@arm.com
Diffstat (limited to 'kernel/sched/debug.c')
| -rw-r--r-- | kernel/sched/debug.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 0c5ec2776ddf..7e08e3d947c2 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -388,6 +388,13 @@ void update_sched_domain_debugfs(void) { int cpu, i; + /* + * This can unfortunately be invoked before sched_debug_init() creates + * the debug directory. Don't touch sd_sysctl_cpus until then. + */ + if (!debugfs_sched) + return; + if (!cpumask_available(sd_sysctl_cpus)) { if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL)) return; |