Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On Thu, Dec 15, 2016 at 3:16 PM, Dave Young wrote:
> Hi, Pingfan
> On 12/14/16 at 02:11pm, Pingfan Liu wrote:
>> kexec-tools always allocates program headers for each possible cpu. This
>> incurs zero PT_NOTE for offline cpu. We mark this case so that later,
>> the capture kernel can distinguish it from the mistake of allocated
>> program header.
>> The counterpart of the capture kernel comes in next patch.
>
> I thought you saw the warnings on ppc64 and it might be a ppc64 issue.
It affects all archs, since kexec-tools creates each program header
for each _present_ cpu. So if the cpu is offline, then the warning
buzzes.
> But if this is instead a general issue, can we think about if this is
> really necessary?
>
> Does it have any side effect other than the warning messages? If there
> is nothing bad other than the warnings maybe leave it as is will be
> a better way.
>
I think kernel warning always made people upset who do not know the
back ground of the related field.
While on the other hand, the program behaves correctly against our
expectation, so just suppress the warning to make everyone easy.
Regards,
Pingfan
>>
>> Signed-off-by: Pingfan Liu
>> ---
>> This unnecessary warning buzz on all archs when there is offline cpu
>>
>> include/uapi/linux/elf.h | 1 +
>> kernel/kexec_core.c | 9 +
>> 2 files changed, 10 insertions(+)
>>
>> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
>> index b59ee07..9744f1e 100644
>> --- a/include/uapi/linux/elf.h
>> +++ b/include/uapi/linux/elf.h
>> @@ -367,6 +367,7 @@ typedef struct elf64_shdr {
>> * using the corresponding note types via the PTRACE_GETREGSET and
>> * PTRACE_SETREGSET requests.
>> */
>> +#define NT_DUMMY 0
>> #define NT_PRSTATUS 1
>> #define NT_PRFPREG 2
>> #define NT_PRPSINFO 3
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 5616755..aeac16e 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -891,9 +891,12 @@ void __crash_kexec(struct pt_regs *regs)
>> if (mutex_trylock(&kexec_mutex)) {
>> if (kexec_crash_image) {
>> struct pt_regs fixed_regs;
>> + unsigned int cpu;
>>
>> crash_setup_regs(&fixed_regs, regs);
>> crash_save_vmcoreinfo();
>> + for_each_cpu_not(cpu, cpu_online_mask)
>> + crash_save_cpu(NULL, cpu);
>> machine_crash_shutdown(&fixed_regs);
>> machine_kexec(kexec_crash_image);
>> }
>> @@ -1040,6 +1043,12 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
>> buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
>> if (!buf)
>> return;
>> + if (regs == NULL) {
>> + buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_DUMMY,
>> + NULL, 0);
>> + final_note(buf);
>> + return;
>> + }
>> memset(&prstatus, 0, sizeof(prstatus));
>> prstatus.pr_pid = current->pid;
>> elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
>> --
>> 2.7.4
>>
>
> Thanks
> Dave
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Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
Hi, Pingfan
On 12/14/16 at 02:11pm, Pingfan Liu wrote:
> kexec-tools always allocates program headers for each possible cpu. This
> incurs zero PT_NOTE for offline cpu. We mark this case so that later,
> the capture kernel can distinguish it from the mistake of allocated
> program header.
> The counterpart of the capture kernel comes in next patch.
I thought you saw the warnings on ppc64 and it might be a ppc64 issue.
But if this is instead a general issue, can we think about if this is
really necessary?
Does it have any side effect other than the warning messages? If there
is nothing bad other than the warnings maybe leave it as is will be
a better way.
>
> Signed-off-by: Pingfan Liu
> ---
> This unnecessary warning buzz on all archs when there is offline cpu
>
> include/uapi/linux/elf.h | 1 +
> kernel/kexec_core.c | 9 +
> 2 files changed, 10 insertions(+)
>
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index b59ee07..9744f1e 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -367,6 +367,7 @@ typedef struct elf64_shdr {
> * using the corresponding note types via the PTRACE_GETREGSET and
> * PTRACE_SETREGSET requests.
> */
> +#define NT_DUMMY 0
> #define NT_PRSTATUS 1
> #define NT_PRFPREG 2
> #define NT_PRPSINFO 3
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..aeac16e 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -891,9 +891,12 @@ void __crash_kexec(struct pt_regs *regs)
> if (mutex_trylock(&kexec_mutex)) {
> if (kexec_crash_image) {
> struct pt_regs fixed_regs;
> + unsigned int cpu;
>
> crash_setup_regs(&fixed_regs, regs);
> crash_save_vmcoreinfo();
> + for_each_cpu_not(cpu, cpu_online_mask)
> + crash_save_cpu(NULL, cpu);
> machine_crash_shutdown(&fixed_regs);
> machine_kexec(kexec_crash_image);
> }
> @@ -1040,6 +1043,12 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
> buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
> if (!buf)
> return;
> + if (regs == NULL) {
> + buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_DUMMY,
> + NULL, 0);
> + final_note(buf);
> + return;
> + }
> memset(&prstatus, 0, sizeof(prstatus));
> prstatus.pr_pid = current->pid;
> elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
> --
> 2.7.4
>
Thanks
Dave
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Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On 12/14/2016 at 05:13 PM, Liu ping fan wrote: > [...] >>> No. This patch just place a mark on these offline cpu. The next patch >>> for capture kernel will recognize this case, and ignore this kind of >>> pt_note by the code: >>> real_sz = 0; // although the size of this kind of PT_NOTE is not zero, >>> but it contains nothing useful, so just ignore it >>> phdr_ptr->p_memsz = real_sz >> If there is any other vmcore functional issue besides throwing "Warning: >> Zero PT_NOTE entries found"? >> > Not at present when I debugged. Well, agree that we should fix it given that it produces many unnecessary warnings on some machines. > I just think we can not suppose the behaviour of different archs, so > just mark out the dummy pt_note. If some archs want to use these notes > memory, > they will just overwrite the dummy. For cpu crash_notes, it should be arch-independent, and related to elf format. > > Thx, > Pingfan > > ___ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
[...] >>> >> No. This patch just place a mark on these offline cpu. The next patch >> for capture kernel will recognize this case, and ignore this kind of >> pt_note by the code: >> real_sz = 0; // although the size of this kind of PT_NOTE is not zero, >> but it contains nothing useful, so just ignore it >> phdr_ptr->p_memsz = real_sz > > If there is any other vmcore functional issue besides throwing "Warning: Zero > PT_NOTE entries found"? > Not at present when I debugged. I just think we can not suppose the behaviour of different archs, so just mark out the dummy pt_note. If some archs want to use these notes memory, they will just overwrite the dummy. Thx, Pingfan ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On 12/14/2016 at 04:56 PM, Liu ping fan wrote: > On Wed, Dec 14, 2016 at 4:48 PM, Xunlei Pang wrote: >> On 12/14/2016 at 02:11 PM, Pingfan Liu wrote: >>> kexec-tools always allocates program headers for each possible cpu. This >>> incurs zero PT_NOTE for offline cpu. We mark this case so that later, >>> the capture kernel can distinguish it from the mistake of allocated >>> program header. >>> The counterpart of the capture kernel comes in next patch. >> Hmm, we can initialize the cpu crash note buf in crash_notes_memory_init(), >> needless >> to do it at the crash moment, right? >> > The cpus can be on-off-on.., We can not know the user's action. I meant we can add the fake note into the cpu note buf, then the crash happens, the online ones will be overwritten with the real note data, while others(!online) will still be the fake note. > >> BTW, does this cause any issue, for example the crash utility can't parse >> the vmcore >> properly? or just reproduce lots of warnings after offline multiple cpus? >> > No. This patch just place a mark on these offline cpu. The next patch > for capture kernel will recognize this case, and ignore this kind of > pt_note by the code: > real_sz = 0; // although the size of this kind of PT_NOTE is not zero, > but it contains nothing useful, so just ignore it > phdr_ptr->p_memsz = real_sz If there is any other vmcore functional issue besides throwing "Warning: Zero PT_NOTE entries found"? Regards, Xunlei ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
[...] >> >> > >> >> > When you execute dmesg on your testing machine and grep nr_cpu_ids, >> >> > what's the value of nr_cpu_ids? >> >> > >> >> nr_cpu_ids=128 >> > >> > And what's the cpu number of in "lscpu" command? >> >> NUMA node1 CPU(s): 0-7 >> >> The system booted up with 128 possible cpu and only 8 online. >> Also I tested on x86 guest, after bootup with 8 cpus, then offline 4 >> of them, the zero PT_NOTE warning buzz too. > > Yes, this is what I think not quite appropriate using > for_each_cpu_not(cpu, cpu_online_mask). Maybe it need try to save on > those cpus which is present but not online. not online seems not good, > it's not reasonable to save those getting apic but no cpu plugged. > In the file:kexec-tools/kexec/crashdump-elf.c nr_cpus = sysconf(_SC_NPROCESSORS_CONF); And this is why this patch needs to make a mark on these offline cpu. This is no something like "_SC_NPROCESSORS_PRESENT" option, so just work around it in kernel side. Anyway for crash kernel, we only write "core" in percpu notes without no more info, and it costs nothing when capture kernel gather the PT_NOTE. Thx, Pingfan ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On Wed, Dec 14, 2016 at 4:48 PM, Xunlei Pang wrote: > On 12/14/2016 at 02:11 PM, Pingfan Liu wrote: >> kexec-tools always allocates program headers for each possible cpu. This >> incurs zero PT_NOTE for offline cpu. We mark this case so that later, >> the capture kernel can distinguish it from the mistake of allocated >> program header. >> The counterpart of the capture kernel comes in next patch. > > Hmm, we can initialize the cpu crash note buf in crash_notes_memory_init(), > needless > to do it at the crash moment, right? > The cpus can be on-off-on.., We can not know the user's action. > BTW, does this cause any issue, for example the crash utility can't parse the > vmcore > properly? or just reproduce lots of warnings after offline multiple cpus? > No. This patch just place a mark on these offline cpu. The next patch for capture kernel will recognize this case, and ignore this kind of pt_note by the code: real_sz = 0; // although the size of this kind of PT_NOTE is not zero, but it contains nothing useful, so just ignore it phdr_ptr->p_memsz = real_sz Thx, Pingfan ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On 12/14/2016 at 02:11 PM, Pingfan Liu wrote:
> kexec-tools always allocates program headers for each possible cpu. This
> incurs zero PT_NOTE for offline cpu. We mark this case so that later,
> the capture kernel can distinguish it from the mistake of allocated
> program header.
> The counterpart of the capture kernel comes in next patch.
Hmm, we can initialize the cpu crash note buf in crash_notes_memory_init(),
needless
to do it at the crash moment, right?
BTW, does this cause any issue, for example the crash utility can't parse the
vmcore
properly? or just reproduce lots of warnings after offline multiple cpus?
Regards,
Xunlei
>
> Signed-off-by: Pingfan Liu
> ---
> This unnecessary warning buzz on all archs when there is offline cpu
>
> include/uapi/linux/elf.h | 1 +
> kernel/kexec_core.c | 9 +
> 2 files changed, 10 insertions(+)
>
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index b59ee07..9744f1e 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -367,6 +367,7 @@ typedef struct elf64_shdr {
> * using the corresponding note types via the PTRACE_GETREGSET and
> * PTRACE_SETREGSET requests.
> */
> +#define NT_DUMMY 0
> #define NT_PRSTATUS 1
> #define NT_PRFPREG 2
> #define NT_PRPSINFO 3
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..aeac16e 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -891,9 +891,12 @@ void __crash_kexec(struct pt_regs *regs)
> if (mutex_trylock(&kexec_mutex)) {
> if (kexec_crash_image) {
> struct pt_regs fixed_regs;
> + unsigned int cpu;
>
> crash_setup_regs(&fixed_regs, regs);
> crash_save_vmcoreinfo();
> + for_each_cpu_not(cpu, cpu_online_mask)
> + crash_save_cpu(NULL, cpu);
> machine_crash_shutdown(&fixed_regs);
> machine_kexec(kexec_crash_image);
> }
> @@ -1040,6 +1043,12 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
> buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
> if (!buf)
> return;
> + if (regs == NULL) {
> + buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_DUMMY,
> + NULL, 0);
> + final_note(buf);
> + return;
> + }
> memset(&prstatus, 0, sizeof(prstatus));
> prstatus.pr_pid = current->pid;
> elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
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Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On 12/14/16 at 04:39pm, Liu ping fan wrote: > On Wed, Dec 14, 2016 at 4:25 PM, Baoquan He wrote: > > On 12/14/16 at 04:15pm, Liu ping fan wrote: > >> On Wed, Dec 14, 2016 at 3:40 PM, Baoquan He wrote: > >> > On 12/14/16 at 02:11pm, Pingfan Liu wrote: > >> >> kexec-tools always allocates program headers for each possible cpu. This > >> >> incurs zero PT_NOTE for offline cpu. We mark this case so that later, > >> >> the capture kernel can distinguish it from the mistake of allocated > >> >> program header. > >> >> The counterpart of the capture kernel comes in next patch. > >> > > >> > When you execute dmesg on your testing machine and grep nr_cpu_ids, > >> > what's the value of nr_cpu_ids? > >> > > >> nr_cpu_ids=128 > > > > And what's the cpu number of in "lscpu" command? > > NUMA node1 CPU(s): 0-7 > > The system booted up with 128 possible cpu and only 8 online. > Also I tested on x86 guest, after bootup with 8 cpus, then offline 4 > of them, the zero PT_NOTE warning buzz too. Yes, this is what I think not quite appropriate using for_each_cpu_not(cpu, cpu_online_mask). Maybe it need try to save on those cpus which is present but not online. not online seems not good, it's not reasonable to save those getting apic but no cpu plugged. Thanks Baoquan ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On Wed, Dec 14, 2016 at 4:25 PM, Baoquan He wrote: > On 12/14/16 at 04:15pm, Liu ping fan wrote: >> On Wed, Dec 14, 2016 at 3:40 PM, Baoquan He wrote: >> > On 12/14/16 at 02:11pm, Pingfan Liu wrote: >> >> kexec-tools always allocates program headers for each possible cpu. This >> >> incurs zero PT_NOTE for offline cpu. We mark this case so that later, >> >> the capture kernel can distinguish it from the mistake of allocated >> >> program header. >> >> The counterpart of the capture kernel comes in next patch. >> > >> > When you execute dmesg on your testing machine and grep nr_cpu_ids, >> > what's the value of nr_cpu_ids? >> > >> nr_cpu_ids=128 > > And what's the cpu number of in "lscpu" command? NUMA node1 CPU(s): 0-7 The system booted up with 128 possible cpu and only 8 online. Also I tested on x86 guest, after bootup with 8 cpus, then offline 4 of them, the zero PT_NOTE warning buzz too. ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On 12/14/16 at 04:15pm, Liu ping fan wrote: > On Wed, Dec 14, 2016 at 3:40 PM, Baoquan He wrote: > > On 12/14/16 at 02:11pm, Pingfan Liu wrote: > >> kexec-tools always allocates program headers for each possible cpu. This > >> incurs zero PT_NOTE for offline cpu. We mark this case so that later, > >> the capture kernel can distinguish it from the mistake of allocated > >> program header. > >> The counterpart of the capture kernel comes in next patch. > > > > When you execute dmesg on your testing machine and grep nr_cpu_ids, > > what's the value of nr_cpu_ids? > > > nr_cpu_ids=128 And what's the cpu number of in "lscpu" command? ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On Wed, Dec 14, 2016 at 3:40 PM, Baoquan He wrote: > On 12/14/16 at 02:11pm, Pingfan Liu wrote: >> kexec-tools always allocates program headers for each possible cpu. This >> incurs zero PT_NOTE for offline cpu. We mark this case so that later, >> the capture kernel can distinguish it from the mistake of allocated >> program header. >> The counterpart of the capture kernel comes in next patch. > > When you execute dmesg on your testing machine and grep nr_cpu_ids, > what's the value of nr_cpu_ids? > nr_cpu_ids=128 ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On 12/14/16 at 02:11pm, Pingfan Liu wrote:
> kexec-tools always allocates program headers for each possible cpu. This
> incurs zero PT_NOTE for offline cpu. We mark this case so that later,
> the capture kernel can distinguish it from the mistake of allocated
> program header.
> The counterpart of the capture kernel comes in next patch.
When you execute dmesg on your testing machine and grep nr_cpu_ids,
what's the value of nr_cpu_ids?
>
> Signed-off-by: Pingfan Liu
> ---
> This unnecessary warning buzz on all archs when there is offline cpu
>
> include/uapi/linux/elf.h | 1 +
> kernel/kexec_core.c | 9 +
> 2 files changed, 10 insertions(+)
>
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index b59ee07..9744f1e 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -367,6 +367,7 @@ typedef struct elf64_shdr {
> * using the corresponding note types via the PTRACE_GETREGSET and
> * PTRACE_SETREGSET requests.
> */
> +#define NT_DUMMY 0
> #define NT_PRSTATUS 1
> #define NT_PRFPREG 2
> #define NT_PRPSINFO 3
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..aeac16e 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -891,9 +891,12 @@ void __crash_kexec(struct pt_regs *regs)
> if (mutex_trylock(&kexec_mutex)) {
> if (kexec_crash_image) {
> struct pt_regs fixed_regs;
> + unsigned int cpu;
>
> crash_setup_regs(&fixed_regs, regs);
> crash_save_vmcoreinfo();
> + for_each_cpu_not(cpu, cpu_online_mask)
> + crash_save_cpu(NULL, cpu);
> machine_crash_shutdown(&fixed_regs);
> machine_kexec(kexec_crash_image);
> }
> @@ -1040,6 +1043,12 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
> buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
> if (!buf)
> return;
> + if (regs == NULL) {
> + buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_DUMMY,
> + NULL, 0);
> + final_note(buf);
> + return;
> + }
> memset(&prstatus, 0, sizeof(prstatus));
> prstatus.pr_pid = current->pid;
> elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
> --
> 2.7.4
>
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Re: [PATCH 1/2] kexec: add a dummy note for each offline cpu
On Wed, Dec 14, 2016 at 2:11 PM, Pingfan Liu wrote:
> kexec-tools always allocates program headers for each possible cpu. This
The code is in the file:kexec-tools/kexec/crashdump-elf.c
nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
> incurs zero PT_NOTE for offline cpu. We mark this case so that later,
> the capture kernel can distinguish it from the mistake of allocated
> program header.
> The counterpart of the capture kernel comes in next patch.
>
> Signed-off-by: Pingfan Liu
> ---
> This unnecessary warning buzz on all archs when there is offline cpu
>
> include/uapi/linux/elf.h | 1 +
> kernel/kexec_core.c | 9 +
> 2 files changed, 10 insertions(+)
>
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index b59ee07..9744f1e 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -367,6 +367,7 @@ typedef struct elf64_shdr {
> * using the corresponding note types via the PTRACE_GETREGSET and
> * PTRACE_SETREGSET requests.
> */
> +#define NT_DUMMY 0
> #define NT_PRSTATUS1
> #define NT_PRFPREG 2
> #define NT_PRPSINFO3
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..aeac16e 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -891,9 +891,12 @@ void __crash_kexec(struct pt_regs *regs)
> if (mutex_trylock(&kexec_mutex)) {
> if (kexec_crash_image) {
> struct pt_regs fixed_regs;
> + unsigned int cpu;
>
> crash_setup_regs(&fixed_regs, regs);
> crash_save_vmcoreinfo();
> + for_each_cpu_not(cpu, cpu_online_mask)
> + crash_save_cpu(NULL, cpu);
> machine_crash_shutdown(&fixed_regs);
> machine_kexec(kexec_crash_image);
> }
> @@ -1040,6 +1043,12 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
> buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
> if (!buf)
> return;
> + if (regs == NULL) {
> + buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_DUMMY,
> + NULL, 0);
> + final_note(buf);
> + return;
> + }
> memset(&prstatus, 0, sizeof(prstatus));
> prstatus.pr_pid = current->pid;
> elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
> --
> 2.7.4
>
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[PATCH 1/2] kexec: add a dummy note for each offline cpu
kexec-tools always allocates program headers for each possible cpu. This
incurs zero PT_NOTE for offline cpu. We mark this case so that later,
the capture kernel can distinguish it from the mistake of allocated
program header.
The counterpart of the capture kernel comes in next patch.
Signed-off-by: Pingfan Liu
---
This unnecessary warning buzz on all archs when there is offline cpu
include/uapi/linux/elf.h | 1 +
kernel/kexec_core.c | 9 +
2 files changed, 10 insertions(+)
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index b59ee07..9744f1e 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -367,6 +367,7 @@ typedef struct elf64_shdr {
* using the corresponding note types via the PTRACE_GETREGSET and
* PTRACE_SETREGSET requests.
*/
+#define NT_DUMMY 0
#define NT_PRSTATUS1
#define NT_PRFPREG 2
#define NT_PRPSINFO3
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 5616755..aeac16e 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -891,9 +891,12 @@ void __crash_kexec(struct pt_regs *regs)
if (mutex_trylock(&kexec_mutex)) {
if (kexec_crash_image) {
struct pt_regs fixed_regs;
+ unsigned int cpu;
crash_setup_regs(&fixed_regs, regs);
crash_save_vmcoreinfo();
+ for_each_cpu_not(cpu, cpu_online_mask)
+ crash_save_cpu(NULL, cpu);
machine_crash_shutdown(&fixed_regs);
machine_kexec(kexec_crash_image);
}
@@ -1040,6 +1043,12 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
if (!buf)
return;
+ if (regs == NULL) {
+ buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_DUMMY,
+ NULL, 0);
+ final_note(buf);
+ return;
+ }
memset(&prstatus, 0, sizeof(prstatus));
prstatus.pr_pid = current->pid;
elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
--
2.7.4
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