drm/radeon: add a force flush to delay work when radeon

Summary

In the Linux kernel, the following vulnerability has been resolved: drm/radeon: add a force flush to delay work when radeon Although radeon card fence and wait for gpu to finish processing current batch rings, there is still a corner case that radeon lockup work queue may not be fully flushed, and meanwhile the radeon_suspend_kms() function has called pci_set_power_state() to put device in D3hot state. Per PCI spec rev 4.0 on 5.3.1.4.1 D3hot State. > Configuration and Message requests are the only TLPs accepted by a Function in > the D3hot state. All other received Requests must be handled as Unsupported Requests, > and all received Completions may optionally be handled as Unexpected Completions. This issue will happen in following logs: Unable to handle kernel paging request at virtual address 00008800e0008010 CPU 0 kworker/0:3(131): Oops 0 pc = [<ffffffff811bea5c>] ra = [<ffffffff81240844>] ps = 0000 Tainted: G W pc is at si_gpu_check_soft_reset+0x3c/0x240 ra is at si_dma_is_lockup+0x34/0xd0 v0 = 0000000000000000 t0 = fff08800e0008010 t1 = 0000000000010000 t2 = 0000000000008010 t3 = fff00007e3c00000 t4 = fff00007e3c00258 t5 = 000000000000ffff t6 = 0000000000000001 t7 = fff00007ef078000 s0 = fff00007e3c016e8 s1 = fff00007e3c00000 s2 = fff00007e3c00018 s3 = fff00007e3c00000 s4 = fff00007fff59d80 s5 = 0000000000000000 s6 = fff00007ef07bd98 a0 = fff00007e3c00000 a1 = fff00007e3c016e8 a2 = 0000000000000008 a3 = 0000000000000001 a4 = 8f5c28f5c28f5c29 a5 = ffffffff810f4338 t8 = 0000000000000275 t9 = ffffffff809b66f8 t10 = ff6769c5d964b800 t11= 000000000000b886 pv = ffffffff811bea20 at = 0000000000000000 gp = ffffffff81d89690 sp = 00000000aa814126 Disabling lock debugging due to kernel taint Trace: [<ffffffff81240844>] si_dma_is_lockup+0x34/0xd0 [<ffffffff81119610>] radeon_fence_check_lockup+0xd0/0x290 [<ffffffff80977010>] process_one_work+0x280/0x550 [<ffffffff80977350>] worker_thread+0x70/0x7c0 [<ffffffff80977410>] worker_thread+0x130/0x7c0 [<ffffffff80982040>] kthread+0x200/0x210 [<ffffffff809772e0>] worker_thread+0x0/0x7c0 [<ffffffff80981f8c>] kthread+0x14c/0x210 [<ffffffff80911658>] ret_from_kernel_thread+0x18/0x20 [<ffffffff80981e40>] kthread+0x0/0x210 Code: ad3e0008 43f0074a ad7e0018 ad9e0020 8c3001e8 40230101 <88210000> 4821ed21 So force lockup work queue flush to fix this problem.