内核 panic 流程 - #5
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详细整理了 Linux 内核 panic 的完整流程，包括： - panic 触发来源 (oops/直接调用/NMI) - vpanic() 核心流程 15 个步骤详解 - 多 CPU 同步机制 (panic_cpu 原子变量) - kdump/kexec 路径分析 - panic notifier 机制 - 关键配置参数和 sysctl 接口 - Oops vs Panic 区别 - WARN → Panic 路径 - 关键数据结构和源码文件索引 Co-authored-by: Slim6882 <jackYoung0915@users.noreply.github.com>
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If revalidating the zones of a zoned block device with
blk_revalidate_disk_zones() fails during a SCSI disk rescan, the following
lockdep splat is thrown:
[ 347.251859] [ T11230] sda: failed to revalidate zones
[ 347.261380] [ T11230] ======================================================
[ 347.263882] [ T11230] WARNING: possible circular locking dependency detected
[ 347.266353] [ T11230] 7.1.0+ #1194 Not tainted
[ 347.268052] [ T11230] ------------------------------------------------------
[ 347.270537] [ T11230] tcsh/11230 is trying to acquire lock:
[ 347.272555] [ T11230] ffffffff8f91d400 (wq_pool_mutex){+.+.}-{4:4}, at: destroy_workqueue+0x15d/0x8d0
[ 347.275914] [ T11230]
but task is already holding lock:
[ 347.278646] [ T11230] ffff88812fa1bcc0 (&q->q_usage_counter(io)#5){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x16/0x30
[ 347.282503] [ T11230]
which lock already depends on the new lock.
[ 347.286239] [ T11230]
the existing dependency chain (in reverse order) is:
[ 347.289408] [ T11230]
-> #2 (&q->q_usage_counter(io)#5){++++}-{0:0}:
[ 347.292437] [ T11230] blk_alloc_queue+0x5ca/0x750
[ 347.294379] [ T11230] blk_mq_alloc_queue+0x14c/0x240
[ 347.296375] [ T11230] scsi_alloc_sdev+0x871/0xd10 [scsi_mod]
[ 347.298619] [ T11230] scsi_probe_and_add_lun+0x600/0xc50 [scsi_mod]
[ 347.301056] [ T11230] __scsi_scan_target+0x187/0x3b0 [scsi_mod]
[ 347.303385] [ T11230] scsi_scan_channel+0xf2/0x180 [scsi_mod]
[ 347.305651] [ T11230] scsi_scan_host_selected+0x20b/0x2d0 [scsi_mod]
[ 347.308119] [ T11230] do_scan_async+0x42/0x420 [scsi_mod]
[ 347.310276] [ T11230] async_run_entry_fn+0x94/0x5a0
[ 347.312284] [ T11230] process_one_work+0x8da/0x1690
[ 347.314287] [ T11230] worker_thread+0x5fe/0x1010
[ 347.316216] [ T11230] kthread+0x358/0x450
[ 347.317675] [ T11230] ret_from_fork+0x5b9/0x8e0
[ 347.319181] [ T11230] ret_from_fork_asm+0x11/0x20
[ 347.320778] [ T11230]
-> #1 (fs_reclaim){+.+.}-{0:0}:
[ 347.322890] [ T11230] fs_reclaim_acquire+0xd5/0x120
[ 347.324464] [ T11230] __kmalloc_cache_node_noprof+0x39/0x620
[ 347.326223] [ T11230] init_rescuer+0x19b/0x560
[ 347.327697] [ T11230] workqueue_init+0x33b/0x6a0
[ 347.329224] [ T11230] kernel_init_freeable+0x2eb/0x600
[ 347.330881] [ T11230] kernel_init+0x1c/0x140
[ 347.332334] [ T11230] ret_from_fork+0x5b9/0x8e0
[ 347.333847] [ T11230] ret_from_fork_asm+0x11/0x20
[ 347.335360] [ T11230]
-> #0 (wq_pool_mutex){+.+.}-{4:4}:
[ 347.337510] [ T11230] __lock_acquire+0xdea/0x2260
[ 347.339030] [ T11230] lock_acquire+0x187/0x2f0
[ 347.340495] [ T11230] __mutex_lock+0x1ab/0x2600
[ 347.341464] [ T11230] destroy_workqueue+0x15d/0x8d0
[ 347.342485] [ T11230] disk_free_zone_resources+0xd5/0x560
[ 347.343577] [ T11230] blk_revalidate_disk_zones+0x620/0xac7
[ 347.344723] [ T11230] sd_zbc_revalidate_zones+0x1dd/0x790 [sd_mod]
[ 347.345938] [ T11230] sd_revalidate_disk+0xc66/0x8e60 [sd_mod]
[ 347.347112] [ T11230] scsi_rescan_device+0x1f9/0x310 [scsi_mod]
[ 347.348318] [ T11230] store_rescan_field+0x19/0x20 [scsi_mod]
[ 347.349507] [ T11230] kernfs_fop_write_iter+0x3d2/0x5e0
[ 347.350565] [ T11230] vfs_write+0x469/0x1000
[ 347.351484] [ T11230] ksys_write+0x116/0x250
[ 347.352403] [ T11230] do_syscall_64+0xf0/0x6e0
[ 347.353361] [ T11230] entry_SYSCALL_64_after_hwframe+0x4b/0x53
[ 347.354533] [ T11230]
other info that might help us debug this:
[ 347.356432] [ T11230] Chain exists of:
wq_pool_mutex --> fs_reclaim --> &q->q_usage_counter(io)#5
[ 347.358919] [ T11230] Possible unsafe locking scenario:
[ 347.360307] [ T11230] CPU0 CPU1
[ 347.361327] [ T11230] ---- ----
[ 347.362340] [ T11230] lock(&q->q_usage_counter(io)#5);
[ 347.363344] [ T11230] lock(fs_reclaim);
[ 347.364526] [ T11230] lock(&q->q_usage_counter(io)#5);
[ 347.365968] [ T11230] lock(wq_pool_mutex);
[ 347.366811] [ T11230]
*** DEADLOCK ***
This happens because SCSI disk rescan is executed from a work context
and a failure of blk_revalidate_disk_zones() causes a call to
disk_free_zone_resources() which will free the disk zone write plug
workqueue.
Avoid this by delaying the destruction of the disk zone write plug
workqueue to disk_release(). Do this by introducing the function
disk_release_zone_resources() and using this new function from
disk_release(). This new function destroys the zone write plugs workqueue
and calls disk_free_zone_resources(), thus allowing to remove the call to
destroy_workqueue() from disk_free_zone_resources().
disk_alloc_zone_resources() is modified to not create the disk zone
write plug work queue if it already exists.
Fixes: a8f59e5 ("block: use a per disk workqueue for zone write plugging")
Cc: stable@vger.kernek.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@kernel.org>
Link: https://patch.msgid.link/20260701082155.1369996-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add
docs/kernel-panic-flow.mdto document the Linux kernel panic process.