Messages in this thread | | | Date | Thu, 25 Feb 2016 19:31:37 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [linux-next, x86_64] no backtrace after "printk/nmi: generic solution for safe printk in NMI" |
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On (02/25/16 18:46), Sergey Senozhatsky wrote: > Hello Petr, > > seem that commit b927968830676373caf4241e80d8b447133f84b2 > Author: Petr Mladek <pmladek@suse.com> > Date: Thu Feb 25 13:00:35 2016 +1100 > > printk/nmi: generic solution for safe printk in NMI > > printk() takes some locks and could not be used a safe way in NMI context. > > The chance of a deadlock is real especially when printing stacks from all > CPUs. This particular problem has been addressed on x86 by the commit > a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs"). > > The patchset brings two big advantages. First, it makes the NMI > backtraces safe on all architectures for free. Second, it makes all NMI > messages almost safe on all architectures (the temporary buffer is > limited. We still should keep the number of messages in NMI context at > minimum). > [..] > > > makes my x86_64 boxen unhappy, I see no CPU backtraces and no panic messages > on HARDLOCKUPs (CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE=1). > > does it work for you?
just for note,
I reverted (next-20160225) the following commits:
bdcdb76696402e1a0821db6bcccb2b4de4049f27 7ad17383fa428d1c89d2be95d00806f33df69dfd 054a26c149a5add6d27d154f2025ee2605d9f25d c2dbc8fd415835a71b0dee0f3f3a353d116f8731 3fd57f62ac2a8de6b402bf5f6aeb3a7d1e3f11a3 3ff0033c1e878b8bd8fce6efcd1b432b24f1d321
-- still no HARDLOCKUP panic backtraces on a console.
reverting of
b927968830676373caf4241e80d8b447133f84b2 (plus MIPS config conflict resolution)
-- fixed the problem for me. I've tested several times.
the sample code that I use for testing is very simple (well.. but it does the job):
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u64 s, e; unsigned long flags;
local_irq_save(flags); s = local_clock() >> 31UL; pr_err(">>>>>>>>>>>>>>>>>START_THE_TEST\n"); while (1) { e = local_clock() >> 31UL; if (e - s > %%YOUR_WATCHDOG_THRESHOLD%%) goto out; } out: pr_err(">>>>>>>>>>>>>>>>>END_THE_TEST\n"); local_irq_restore(flags);
---
most likely I'll be able to reply only tomorrow (in case if there will be any questions).
-ss
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