In the Linux kernel, the following vulnerability has been resolved: scsi: hisi_sas: Add cond_resched() for no forced preemption model For no forced preemption model kernel, in the scenario where the expander is connected to 12 high performance SAS SSDs, the following call trace may occur: [ 214.409199][ C240] watchdog: BUG: soft lockup - CPU#240 stuck for 22s! [irq/149-hisi_sa:3211] [ 214.568533][ C240] pstate: 60400009 (nZCv daif +PAN -UAO -TCO BTYPE=--) [ 214.575224][ C240] pc : fput_many+0x8c/0xdc [ 214.579480][ C240] lr : fput+0x1c/0xf0 [ 214.583302][ C240] sp : ffff80002de2b900 [ 214.587298][ C240] x29: ffff80002de2b900 x28: ffff1082aa412000 [ 214.593291][ C240] x27: ffff3062a0348c08 x26: ffff80003a9f6000 [ 214.599284][ C240] x25: ffff1062bbac5c40 x24: 0000000000001000 [ 214.605277][ C240] x23: 000000000000000a x22: 0000000000000001 [ 214.611270][ C240] x21: 0000000000001000 x20: 0000000000000000 [ 214.617262][ C240] x19: ffff3062a41ae580 x18: 0000000000010000 [ 214.623255][ C240] x17: 0000000000000001 x16: ffffdb3a6efe5fc0 [ 214.629248][ C240] x15: ffffffffffffffff x14: 0000000003ffffff [ 214.635241][ C240] x13: 000000000000ffff x12: 000000000000029c [ 214.641234][ C240] x11: 0000000000000006 x10: ffff80003a9f7fd0 [ 214.647226][ C240] x9 : ffffdb3a6f0482fc x8 : 0000000000000001 [ 214.653219][ C240] x7 : 0000000000000002 x6 : 0000000000000080 [ 214.659212][ C240] x5 : ffff55480ee9b000 x4 : fffffde7f94c6554 [ 214.665205][ C240] x3 : 0000000000000002 x2 : 0000000000000020 [ 214.671198][ C240] x1 : 0000000000000021 x0 : ffff3062a41ae5b8 [ 214.677191][ C240] Call trace: [ 214.680320][ C240] fput_many+0x8c/0xdc [ 214.684230][ C240] fput+0x1c/0xf0 [ 214.687707][ C240] aio_complete_rw+0xd8/0x1fc [ 214.692225][ C240] blkdev_bio_end_io+0x98/0x140 [ 214.696917][ C240] bio_endio+0x160/0x1bc [ 214.701001][ C240] blk_update_request+0x1c8/0x3bc [ 214.705867][ C240] scsi_end_request+0x3c/0x1f0 [ 214.710471][ C240] scsi_io_completion+0x7c/0x1a0 [ 214.715249][ C240] scsi_finish_command+0x104/0x140 [ 214.720200][ C240] scsi_softirq_done+0x90/0x180 [ 214.724892][ C240] blk_mq_complete_request+0x5c/0x70 [ 214.730016][ C240] scsi_mq_done+0x48/0xac [ 214.734194][ C240] sas_scsi_task_done+0xbc/0x16c [libsas] [ 214.739758][ C240] slot_complete_v3_hw+0x260/0x760 [hisi_sas_v3_hw] [ 214.746185][ C240] cq_thread_v3_hw+0xbc/0x190 [hisi_sas_v3_hw] [ 214.752179][ C240] irq_thread_fn+0x34/0xa4 [ 214.756435][ C240] irq_thread+0xc4/0x130 [ 214.760520][ C240] kthread+0x108/0x13c [ 214.764430][ C240] ret_from_fork+0x10/0x18 This is because in the hisi_sas driver, both the hardware interrupt handler and the interrupt thread are executed on the same CPU. In the performance test scenario, function irq_wait_for_interrupt() will always return 0 if lots of interrupts occurs and the CPU will be continuously consumed. As a result, the CPU cannot run the watchdog thread. When the watchdog time exceeds the specified time, call trace occurs. To fix it, add cond_resched() to execute the watchdog thread.
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