lkml.org 
[lkml]   [2022]   [Jul]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 1/2] cpuhp: make target_store() a nop when target == state
Date
writing the current state back in hotplug/target calls cpu_down()
which will set cpu dying even when it isn't and then nothing will
ever clear it. A stress test that reads values and writes them back
for all cpu device files in sysfs will trigger the BUG() in
select_fallback_rq once all cpus are marked as dying.

kernel/cpu.c::target_store()
...
if (st->state < target)
ret = cpu_up(dev->id, target);
else
ret = cpu_down(dev->id, target);

cpu_down() -> cpu_set_state()
bool bringup = st->state < target;
...
if (cpu_dying(cpu) != !bringup)
set_cpu_dying(cpu, !bringup);

Fix this by letting state==target fall through in the target_store()
conditional. Also make sure st->target == target in that case.

Signed-off-by: Phil Auld <pauld@redhat.com>
---
kernel/cpu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index bbad5e375d3b..305694a2ca26 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2326,8 +2326,10 @@ static ssize_t target_store(struct device *dev, struct device_attribute *attr,

if (st->state < target)
ret = cpu_up(dev->id, target);
- else
+ else if (st->state > target)
ret = cpu_down(dev->id, target);
+ else if (st->target != target)
+ st->target = target;
out:
unlock_device_hotplug();
return ret ? ret : count;
--
2.31.1
\
 
 \ /
  Last update: 2022-07-11 23:17    [W:0.064 / U:0.800 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site