Messages in this thread | | | Subject | Re: [PATCH] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores | From | Hoeun Ryu <> | Date | Fri, 4 Aug 2017 22:33:50 +0900 |
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> On 4 Aug 2017, at 8:43 PM, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > >> On Fri, Aug 04, 2017 at 11:38:16AM +0100, James Morse wrote: >> Hi Hoeun, >> >>> On 04/08/17 08:02, Hoeun Ryu wrote: >>> Commit 0ee5941 : (x86/panic: replace smp_send_stop() with kdump friendly >>> version in panic path) introduced crash_smp_send_stop() which is a weak >>> function and can be overriden by architecture codes to fix the side effect >>> caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_ >>> notifiers" option). >> >> If I've understood correctly: if we boot with this option core code doesn't use >> our machine_crash_shutdown(), and instead calls crash_smp_send_stop(), which we > > No. Machine_crash_shutdown() is always called, but at that time, > all the cpus other than the crashing cpu have already died in this case. >
You're right.
>> don't have, so it uses the default smp_send_stop(), which doesn't save the regs. >> >> Thanks for catching this! >> >> >> Could we rename smp_send_crash_stop() crash_smp_send_stop() and add the >> called-twice logic there? They are similar enough that I'm getting them muddled >> already! >> > > Nice.
I'll reflect it in v2. Thank you for the review.
> > -Takahiro AKASHI > >> >> Thanks, >> >> James >> >> >>> ARM64 architecture uses the weak version function and the problem is that >>> the weak function simply calls smp_send_stop() which makes other CPUs >>> offline and takes away the chance to save crash information for nonpanic >>> CPUs in machine_crash_shutdown() when crash_kexec_post_notifiers kernel >>> option is enabled. >>> >>> Calling smp_send_crash_stop() in the function is useless because all >>> nonpanic CPUs are already offline by smp_send_stop() in this case and >>> smp_send_crash_stop() only works against online CPUs. >>> >>> The result is that /proc/vmcore is not available with the error messages; >>> "Warning: Zero PT_NOTE entries found", "Kdump: vmcore not initialized". >>> >>> crash_smp_send_stop() is implemented for ARM64 architecture to fix this >>> problem and the function (strong symbol version) saves crash information >>> for nonpanic CPUs using smp_send_crash_stop() and machine_crash_shutdown() >>> tries to save crash information for nonpanic CPUs only when >>> crash_kexec_post_notifiers kernel option is disabled. >> >>
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