| Message ID | 1501830173-15989-1-git-send-email-hoeun.ryu@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 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! 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.
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. > 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. -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. > >
> On 4 Aug 2017, at 7:38 PM, James Morse <james.morse@arm.com> 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 > 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! I think it is possible, I will reflect it in v2. Thank you for the review. > > 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. > >
> 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. >> >>
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index 481f54a..ec55cd8 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c @@ -213,6 +213,23 @@ void machine_kexec(struct kimage *kimage) BUG(); /* Should never get here. */ } +void crash_smp_send_stop(void) +{ + static int cpus_stopped; + + /* + * This function can be called twice in panic path, but obviously + * we execute this only once. + */ + if (cpus_stopped) + return; + + /* shutdown non-crashing cpus */ + smp_send_crash_stop(); + + cpus_stopped = 1; +} + static void machine_kexec_mask_interrupts(void) { unsigned int i; @@ -252,7 +269,7 @@ void machine_crash_shutdown(struct pt_regs *regs) local_irq_disable(); /* shutdown non-crashing cpus */ - smp_send_crash_stop(); + crash_smp_send_stop(); /* for crashing cpu */ crash_save_cpu(regs, smp_processor_id());
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). 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. Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com> --- arch/arm64/kernel/machine_kexec.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)