Re: [PATCH v2] locking/qspinlock: Do spin-wait in slowpath if preemptible

[Peter Zijlstra]

On Tue, Sep 20, 2022 at 03:55:42PM -0400, Waiman Long wrote:
> There are some code paths in the kernel where arch_spin_lock() will be
> called directly when the lock isn't expected to be contended and critical
> section is short. For example, tracing_saved_cmdlines_size_read()
> in kernel/trace/trace.c does that.
> 
> In most cases, preemption is also not disabled. This creates a problem
> for the qspinlock slowpath which expects preemption to be disabled

Using arch_spin_lock() without disabling preemption is a straight up
bug. Don't work around that.