On (02/25/16 18:46), Sergey Senozhatsky wrote:
> Hello Petr,
>
> seem that commit b927968830676373caf4241e80d8b447133f84b2
> Author: Petr Mladek <[email protected]>
> 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):
---
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
