Hi Doug,

On Fri, Dec 07, 2018 at 10:40:24AM -0800, Doug Anderson wrote:

On Fri, Dec 7, 2018 at 9:42 AM Catalin Marinas [off-list ref] wrote:

quoted

On Tue, Dec 04, 2018 at 07:38:24PM -0800, Douglas Anderson wrote:

quoted

Douglas Anderson (4):
  kgdb: Remove irq flags from roundup
  kgdb: Fix kgdb_roundup_cpus() for arches who used smp_call_function()
  kgdb: Don't round up a CPU that failed rounding up before
  kdb: Don't back trace on a cpu that didn't round up

FWIW, trying these on arm64 (ThunderX2) with CONFIG_KGDB_TESTS_ON_BOOT=y
on top of 4.20-rc5 doesn't boot. It looks like they leave interrupts
disabled when they shouldn't and it trips over the BUG at
mm/vmalloc.c:1380 (called via do_fork -> copy_process).

Now, I don't think these patches make things worse on arm64 since prior
to them the kgdb boot tests on arm64 were stuck in a loop (RUN
singlestep).

Thanks for the report!  ...actually, I'd never tried CONFIG_KGDB_TESTS
before.  ...so I tried them now:

A) chromeos-4.19 tree on qcom-sdm845 without this series: booted up OK
B) chromeos-4.19 tree on qcom-sdm845 with this series: booted up OK
C) v4.20-rc5-90-g30002dd008ed on rockchip-rk3399 (kevin) with this
series: booted up OK

Example output from B) above:

localhost ~ # dmesg | grep kgdbts
[    2.139814] KGDB: Registered I/O driver kgdbts
[    2.144582] kgdbts:RUN plant and detach test
[    2.165333] kgdbts:RUN sw breakpoint test
[    2.172990] kgdbts:RUN bad memory access test
[    2.178640] kgdbts:RUN singlestep test 1000 iterations
[    2.187765] kgdbts:RUN singlestep [0/1000]
[    2.559596] kgdbts:RUN singlestep [100/1000]
[    2.931419] kgdbts:RUN singlestep [200/1000]
[    3.303474] kgdbts:RUN singlestep [300/1000]
[    3.675121] kgdbts:RUN singlestep [400/1000]
[    4.046867] kgdbts:RUN singlestep [500/1000]
[    4.418920] kgdbts:RUN singlestep [600/1000]
[    4.790824] kgdbts:RUN singlestep [700/1000]
[    5.162479] kgdbts:RUN singlestep [800/1000]
[    5.534103] kgdbts:RUN singlestep [900/1000]
[    5.902299] kgdbts:RUN do_fork for 100 breakpoints
[    8.463900] KGDB: Unregistered I/O driver kgdbts, debugger disabled

...so I guess I'm a little confused.  Either I have a different config
than you do or something is special about your machine?

I tried it now on a Juno board both as a host and a guest and boots
fine. It must be something that only triggers ThunderX2. Ignore the
report for now, if I find anything interesting I'll let you know.

-- 
Catalin

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