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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. Signed-off-by: Yihang Li <liyihang9@huawei.com> Link: https://lore.kernel.org/r/20241008021822.2617339-8-liyihang9@huawei.com Reviewed-by: Xiang Chen <chenxiang66@hisilicon.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.