Hey Ryo, On Fri, Feb 21, 2025 at 11:23:28AM +0900, Ryo Takakura wrote: > Hi Hamza! > > On Thu, 20 Feb 2025 17:53:00 -0500, Hamza Mahfooz wrote: > >Since, the panic handlers may require certain cpus to be online to panic > >gracefully, we should call them before turning off SMP. Without this > >re-ordering, on Hyper-V hv_panic_vmbus_unload() times out, because the > >vmbus channel is bound to VMBUS_CONNECT_CPU and unless the crashing cpu > >is the same as VMBUS_CONNECT_CPU, VMBUS_CONNECT_CPU will be offlined by > >crash_smp_send_stop() before the vmbus channel can be deconstructed. > > > >Signed-off-by: Hamza Mahfooz <hamzamahfooz@xxxxxxxxxxxxxxxxxxx> > >--- > > kernel/panic.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > >diff --git a/kernel/panic.c b/kernel/panic.c > >index fbc59b3b64d0..9712a46dfe27 100644 > >--- a/kernel/panic.c > >+++ b/kernel/panic.c > >@@ -372,8 +372,6 @@ void panic(const char *fmt, ...) > > if (!_crash_kexec_post_notifiers) > > __crash_kexec(NULL); > > > >- panic_other_cpus_shutdown(_crash_kexec_post_notifiers); > >- > > printk_legacy_allow_panic_sync(); > > I think printk_legacy_allow_panic_sync() is placed after > panic_other_cpus_shutdown() so that it flushes the stored > cpus backtraces as described [0]. > > > /* > >@@ -382,6 +380,8 @@ void panic(const char *fmt, ...) > > */ > > atomic_notifier_call_chain(&panic_notifier_list, 0, buf); > > > >+ panic_other_cpus_shutdown(_crash_kexec_post_notifiers); > >+ > > So maybe panic_other_cpus_shutdown() should be palced after > atomic_notifier_call_chain() along with printk_legacy_allow_panic_sync() > like below? > > ----- BEGIN ----- > diff --git a/kernel/panic.c b/kernel/panic.c > index d8635d5cecb2..7ac40e85ee27 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -372,16 +372,16 @@ void panic(const char *fmt, ...) > if (!_crash_kexec_post_notifiers) > __crash_kexec(NULL); > > - panic_other_cpus_shutdown(_crash_kexec_post_notifiers); > - > - printk_legacy_allow_panic_sync(); > - > /* > * Run any panic handlers, including those that might need to > * add information to the kmsg dump output. > */ > atomic_notifier_call_chain(&panic_notifier_list, 0, buf); > > + panic_other_cpus_shutdown(_crash_kexec_post_notifiers); > + > + printk_legacy_allow_panic_sync(); > + > panic_print_sys_info(false); > > kmsg_dump_desc(KMSG_DUMP_PANIC, buf); > ----- END ----- Ya, that looks fine to me, that's actually how I had it initally, but I wasn't sure if it had to go before the panic handlers. So, I erred on the side of caution. BR, Hamza > > Sincerely, > Ryo Takakura > > [0] https://lore.kernel.org/all/20240820063001.36405-30-john.ogness@xxxxxxxxxxxxx/
