rcutorture: Fix rcutorture_one_extend_check() splat in RT kernels

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: rcutorture: Fix rcutorture_one_extend_check() splat in RT kernels For built with CONFIG_PREEMPT_RT=y kernels, running rcutorture tests resulted in the following splat: [ 68.797425] rcutorture_one_extend_check during change: Current 0x1 To add 0x1 To remove 0x0 preempt_count() 0x0 [ 68.797533] WARNING: CPU: 2 PID: 512 at kernel/rcu/rcutorture.c:1993 rcutorture_one_extend_check+0x419/0x560 [rcutorture] [ 68.797601] Call Trace: [ 68.797602] <TASK> [ 68.797619] ? lockdep_softirqs_off+0xa5/0x160 [ 68.797631] rcutorture_one_extend+0x18e/0xcc0 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c] [ 68.797646] ? local_clock+0x19/0x40 [ 68.797659] rcu_torture_one_read+0xf0/0x280 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c] [ 68.797678] ? __pfx_rcu_torture_one_read+0x10/0x10 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c] [ 68.797804] ? __pfx_rcu_torture_timer+0x10/0x10 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c] [ 68.797815] rcu-torture: rcu_torture_reader task started [ 68.797824] rcu-torture: Creating rcu_torture_reader task [ 68.797824] rcu_torture_reader+0x238/0x580 [rcutorture 2466dbd2ff34dbaa36049cb323a80c3306ac997c] [ 68.797836] ? kvm_sched_clock_read+0x15/0x30 Disable BH does not change the SOFTIRQ corresponding bits in preempt_count() for RT kernels, this commit therefore use softirq_count() to check the if BH is disabled.

References

• https://git.kernel.org/stable/c/a85550267247cdf5e7499be00ea8e388ab014e50
• https://git.kernel.org/stable/c/69c5ae0f441c2d72e8f48dc1e08464c172360c4c
• https://git.kernel.org/stable/c/8d71351d88e478d3c4e945e3218e97ec677fd807