On 2024/8/20 01:45, Greg KH wrote:
On Mon, Aug 19, 2024 at 10:59:45PM +0800, Wen Yang wrote:
pstore_dump() is called when both preemption and local IRQ are disabled,
and a spinlock is obtained, which is problematic for the RT kernel because
in this configuration, spinlocks are sleep locks.
Replace the spinlock_t with raw_spinlock_t to avoid sleeping in atomic context.
This feels odd, is it only an out-of-tree RT thing? Or does this affect
in-kernel code as well? What prevents any normal spinlock from sleeping
in your system configuration as well?
Thank you for your comment.
If we enable PREEMPT_RT, it will also affect in-kernel code, such as in
the following scenario:
echo b > /proc/sysrq-trigger
- sysrq_handle_reboot
- emergency_restart
- kmsg_dump
- pstore_dump
Obtained psinfo->buf_lock, if there is a lot of error log in the kernel,
it will last for a long time
If the system unexpectedly crashes at this time:
- panic()
- kmsg_dump
- pstore_dump
Attempting to obtain psinfo->buf_lock while disabling interrupts and
preemption, but since this lock is already held by the above process, it
will result in illegal sleep.
--
Best wishes,
Wen
