On 08/19/24 at 09:45am, Sourabh Jain wrote: > Hello Michael and Boaquan > > On 01/08/24 12:21, Sourabh Jain wrote: > > Hello Michael, > > > > On 01/08/24 08:04, Michael Ellerman wrote: > > > Sourabh Jain <sourabhjain@xxxxxxxxxxxxx> writes: > > > > The following errors are observed when kexec is done with SMT=off on > > > > powerpc. > > > > > > > > [ 358.458385] Removing IBM Power 842 compression device > > > > [ 374.795734] kexec_core: Starting new kernel > > > > [ 374.795748] kexec: Waking offline cpu 1. > > > > [ 374.875695] crash hp: kexec_trylock() failed, elfcorehdr may > > > > be inaccurate > > > > [ 374.935833] kexec: Waking offline cpu 2. > > > > [ 375.015664] crash hp: kexec_trylock() failed, elfcorehdr may > > > > be inaccurate > > > > snip.. > > > > [ 375.515823] kexec: Waking offline cpu 6. > > > > [ 375.635667] crash hp: kexec_trylock() failed, elfcorehdr may > > > > be inaccurate > > > > [ 375.695836] kexec: Waking offline cpu 7. > > > Are they actually errors though? Do they block the actual kexec from > > > happening? Or are they just warnings in dmesg? > > > > The kexec kernel boots fine. > > > > This warning appears regardless of whether the kdump kernel is loaded. > > > > However, when the kdump kernel is loaded, we will not be able to update > > the kdump image (FDT). > > I think this should be fine given that kexec is in progress. > > > > Please let me know your opinion. > > > > > Because the fix looks like it could be racy. > > > > It seems like it is racy, but given that kexec takes the lock first and > > then > > brings the CPU up, which triggers the kdump image, which always fails to > > update the kdump image because it could not take the same lock. > > > > Note: the kexec lock is not released unless kexec boot fails. > > Any comments or suggestions on this fix? Is this a little better? diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 63cf89393c6e..0355ffb712f4 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -504,7 +504,7 @@ int crash_check_hotplug_support(void) crash_hotplug_lock(); /* Obtain lock while reading crash information */ - if (!kexec_trylock()) { + if (!kexec_trylock() && kexec_in_progress) { pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n"); crash_hotplug_unlock(); return 0; @@ -539,7 +539,7 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu, crash_hotplug_lock(); /* Obtain lock while changing crash information */ - if (!kexec_trylock()) { + if (!kexec_trylock() && kexec_in_progress) { pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n"); crash_hotplug_unlock(); return; _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec