Messages in this thread | | | From | Sergey Senozhatsky <> | Date | Sat, 13 Jul 2019 15:09:29 +0900 | Subject | Re: [PATCH] kernel/printk: prevent deadlock at calling kmsg_dump from NMI context |
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On (07/12/19 17:54), Konstantin Khlebnikov wrote: > Function kmsg_dump could be invoked from NMI context intentionally or > accidentally because it is called at various oops/panic paths. > Kernel message dumpers are not ready to work in NMI context right now. > They could deadlock on lockbuf_lock or break internal structures.
Hmm. printk()-s from NMI go through per-CPU printk_safe/nmi - a bunch of lockless buffers which is supposed to deal with printk() deadlocks, including NMI printk()-s.
include/linux/hardirq.h
#define nmi_enter() ... printk_nmi_enter(); ...
#define nmi_exit() ... printk_nmi_exit(); ...
So we are not really supposed to deadlock.
-ss
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