Re: [Crash-utility] [crash patch] Compute init_thread_union size

On Thu, 2018-04-05 at 10:01 -0400, Dave Anderson wrote: > > ----- Original Message ----- > > On Thu, 2018-04-05 at 09:27 -0400, Dave Anderson wrote: > > > > > > ----- Original Message ----- > > > > Greetings, > > > > > > > > I know absolutely nothing about how crash maintenance is done, and very > > > > damn little about crash's gizzard, so please consider the below a bug > > > > report, a patch.. or bloody annoying spam, as you see fit. > > > > > > Hi Mike, > > > > > > No, it's most definitely appreciated. Normally patches are posted on the > > > crash utility mailing list (crash-utility(a)redhat.com), but this is fine. > > > > > > And speaking of the mailing list, there was a bug report and subsequent > > > thread yesterday concerning this issue: > > > > > > https://www.redhat.com/archives/crash-utility/2018-April/msg00000.html > > > > > > It was unresolved because the thread_union still exists in the most > > > recent upstream sources, and I can still see the union declaration > > > in the most recent Fedora kernel. > > > > It still exists, but... > > > > homer:..kernel/linux-4.15 # objdump -t vmlinux|grep thread_union > > ffffffff81e00000 g     O .data  0000000000004000 init_thread_union > > ^^^^ > > homer:..kernel/linux-master # objdump -t vmlinux|grep thread_union > > ffffffff81e00000 g       .data  0000000000000000 init_thread_union > > ^^^^ > > > > ...it's size went missing at the referenced commit. > > Right, but the crash utility never dealt with the "init_thread_union" > data symbol, but rather uses the declaration of the "thread_union" > union, which still exists in today's linux-git: > > union thread_union { > #ifndef CONFIG_ARCH_TASK_STRUCT_ON_STACK > struct task_struct task; > #endif > #ifndef CONFIG_THREAD_INFO_IN_TASK > struct thread_info thread_info; > #endif > unsigned long stack[THREAD_SIZE/sizeof(long)]; > }; > > So I'm guessing that the x86_64 arch never references the thread_union > from include/linux/sched.h, and therefore has no need to put it in the > vmlinux debuginfo data? I don't recall all of the troubleshooting details, guess I should have written the changelog at the same time I twiddled the code. I expected patchlet to be a throw away, so it didn't get a changelog until this morning when I happened to notice that virgin source was still broken. -Mike