Kernel panic due to hard lockup when attempting to trigger multiple sysrq-t events

Issue

• NMI watchdog detected hard lockup when issuing multiple SysRg-T magic key sequences.

• The system crashed with the following call traces:

crash> log
[..]
[1141515.690181] Kernel panic - not syncing: Hard LOCKUP
[1141515.690182] CPU: 14 PID: 75114 Comm: peer_down.sh Kdump: loaded Tainted: GOEL ------------ T 3.10.0-1127.18.2.el7.x86_64 #1
[1141515.690183] Hardware name: HPE Synergy 480 Gen10/Synergy 480 Gen10 Compute Module, BIOS I42 03/09/2020
[1141515.690183] Call Trace:
[1141515.690185]  <NMI>  [<ffffffff9637ffa5>] dump_stack+0x19/0x1b
[1141515.690186]  [<ffffffff96379541>] panic+0xe8/0x21f
[1141515.690188]  [<ffffffff96392ed2>] ? system_call_fastpath+0x25/0x2a
[1141515.690191]  [<ffffffff95c9ba6f>] nmi_panic+0x3f/0x40
[1141515.690193]  [<ffffffff95d4f6f1>] watchdog_overflow_callback+0x121/0x140
[1141515.690194]  [<ffffffff95da90e7>] __perf_event_overflow+0x57/0x100
[1141515.690196]  [<ffffffff95db28e4>] perf_event_overflow+0x14/0x20
[1141515.690197]  [<ffffffff95c0a9a0>] handle_pmi_common+0x1a0/0x250
[1141515.690200]  [<ffffffff95c0ac7f>] intel_pmu_handle_irq+0xcf/0x1d0
[1141515.690202]  [<ffffffff96389031>] perf_event_nmi_handler+0x31/0x50
[1141515.690203]  [<ffffffff9638a93c>] nmi_handle.isra.0+0x8c/0x150
[1141515.690205]  [<ffffffff9638ab5d>] do_nmi+0x15d/0x460
[1141515.690207]  [<ffffffff96389d9c>] end_repeat_nmi+0x1e/0x81
[1141515.690213]  [<ffffffffc0491250>] ? sys_imageblit+0x250/0x1000 [sysimgblt]
[1141515.690217]  [<ffffffffc0491250>] ? sys_imageblit+0x250/0x1000 [sysimgblt]
[1141515.690221]  [<ffffffffc0491250>] ? sys_imageblit+0x250/0x1000 [sysimgblt]
[1141515.690228]  <EOE>  [<ffffffffc0553737>] drm_fb_helper_sys_imageblit+0x17/0x40 [drm_kms_helper]
[1141515.690233]  [<ffffffffc053776b>] mga_imageblit+0x1b/0x40 [mgag200]
[1141515.690234]  [<ffffffff9600a62d>] bit_putcs+0x31d/0x5a0
[1141515.690238]  [<ffffffffc053762f>] ? mga_dirty_update+0x1ef/0x310 [mgag200]
[1141515.690242]  [<ffffffffc053777f>] ? mga_imageblit+0x2f/0x40 [mgag200]
[1141515.690244]  [<ffffffff9600a2d3>] ? bit_cursor+0x663/0x6a0
[1141515.690246]  [<ffffffff96005a2b>] fbcon_putcs+0x12b/0x160
[1141515.690247]  [<ffffffff9600a310>] ? bit_cursor+0x6a0/0x6a0
[1141515.690249]  [<ffffffff96005d77>] fbcon_redraw.isra.24+0x197/0x200
[1141515.690250]  [<ffffffff96006ca4>] fbcon_scroll+0x364/0xda0
[1141515.690252]  [<ffffffff9607e1ff>] scrup+0x16f/0x180
[1141515.690253]  [<ffffffff9607e2b0>] lf+0xa0/0xb0
[1141515.690254]  [<ffffffff9607e592>] vt_console_print+0x2d2/0x430
[1141515.690256]  [<ffffffff95c9cfb3>] call_console_drivers.constprop.19+0x93/0xf0
[1141515.690257]  [<ffffffff95c9e7b8>] console_unlock+0x468/0x4b0
[1141515.690258]  [<ffffffff95c9ebc4>] vprintk_emit+0x3c4/0x510
[1141515.690260]  [<ffffffff95c9ef79>] vprintk_default+0x29/0x40
[1141515.690261]  [<ffffffff963796d8>] printk+0x60/0x77
[1141515.690263]  [<ffffffff95cf5cc4>] print_rt_rq+0x214/0x2b0
[1141515.690264]  [<ffffffff95cee055>] print_rt_stats+0x95/0xd0
[1141515.690266]  [<ffffffff95cf45a4>] print_cpu+0x2d4/0xe40
[1141515.690268]  [<ffffffff95cf5d91>] sysrq_sched_debug_show+0x31/0x60
[1141515.690270]  [<ffffffff95cdac29>] show_state_filter+0xa9/0xd0
[1141515.690272]  [<ffffffff96073940>] sysrq_handle_showstate+0x10/0x20
[1141515.690273]  [<ffffffff960740dd>] __handle_sysrq+0x10d/0x170
[1141515.690274]  [<ffffffff96074548>] write_sysrq_trigger+0x28/0x40
[1141515.690276]  [<ffffffff95ec6280>] proc_reg_write+0x40/0x80
[1141515.690277]  [<ffffffff95e4d1d0>] vfs_write+0xc0/0x1f0
[1141515.690279]  [<ffffffff95e4df9f>] SyS_write+0x7f/0xf0
[1141515.690281]  [<ffffffff96392ed2>] system_call_fastpath+0x25/0x2a
[..]