rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent_state()

In the Linux kernel, the following vulnerability has been resolved:

rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent_state()

Running rcutorture with non-zero fqs_duration module parameter in a

kernel built with CONFIG_PREEMPTION=y results in the following splat:

BUG: using __this_cpu_read() in preemptible [00000000]

code: rcu_torture_fqs/398

caller is __this_cpu_preempt_check+0x13/0x20

CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+

Call Trace:

<TASK>

dump_stack_lvl+0x5b/0x86

dump_stack+0x10/0x16

check_preemption_disabled+0xe5/0xf0

__this_cpu_preempt_check+0x13/0x20

rcu_force_quiescent_state.part.0+0x1c/0x170

rcu_force_quiescent_state+0x1e/0x30

rcu_torture_fqs+0xca/0x160

? rcu_torture_boost+0x430/0x430

kthread+0x192/0x1d0

? kthread_complete_and_exit+0x30/0x30

ret_from_fork+0x22/0x30

</TASK>

The problem is that rcu_force_quiescent_state() uses __this_cpu_read()

in preemptible code instead of the proper raw_cpu_read(). This commit

therefore changes __this_cpu_read() to raw_cpu_read().