Bug 264383
| Summary: | SMP: Miss access to a global variable in `smp_rendezvous_action` function. | ||||||
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| Product: | Base System | Reporter: | Yuichiro NAITO <naito.yuichiro> | ||||
| Component: | kern | Assignee: | Mark Johnston <markj> | ||||
| Status: | Closed FIXED | ||||||
| Severity: | Affects Only Me | CC: | emaste, jhb, kib, markj, mjg | ||||
| Priority: | --- | Keywords: | needs-qa | ||||
| Version: | CURRENT | Flags: | koobs:
maintainer-feedback?
(markj) koobs: maintainer-feedback? (mjg) koobs: maintainer-feedback? (kib) koobs: maintainer-feedback? (jhb) koobs: mfc-stable13? koobs: mfc-stable12? |
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| Hardware: | Any | ||||||
| OS: | Any | ||||||
| Attachments: |
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^Triage: Can't identify a suitable key maintainer to this component, request feedback from a few folks who have played with, fixed or improved rendezvous in the recent(ish) past. The patch looks right to me. I'll test and commit it within the next couple of days if no one objects. This seems fine to me. I think it was just a simple oversight in the initial commit that added the locals (f53d15fe1b8a7a7df972f253b38c698f6ca45b71f53d15fe1b8a7a7df972f253b38c698f6ca45b71) A commit in branch main references this bug: URL: https://cgit.FreeBSD.org/src/commit/?id=8d95f500521128c2b40270bdd703a54b56dbccf2 commit 8d95f500521128c2b40270bdd703a54b56dbccf2 Author: Yuichiro NAITO <naito.yuichiro@gmail.com> AuthorDate: 2022-06-06 15:21:33 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2022-06-06 15:29:51 +0000 smp: Use local copies of the setup function pointer and argument No functional change intended. PR: 264383 Reviewed by: jhb, markj MFC after: 1 week sys/kern/subr_smp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) A commit in branch stable/13 references this bug: URL: https://cgit.FreeBSD.org/src/commit/?id=a39788bd281c3b297be37a2df79594c5cbb3ded8 commit a39788bd281c3b297be37a2df79594c5cbb3ded8 Author: Yuichiro NAITO <naito.yuichiro@gmail.com> AuthorDate: 2022-06-06 15:21:33 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2022-06-13 12:43:06 +0000 smp: Use local copies of the setup function pointer and argument No functional change intended. PR: 264383 Reviewed by: jhb, markj (cherry picked from commit 8d95f500521128c2b40270bdd703a54b56dbccf2) sys/kern/subr_smp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Thanks for the patch. |
Created attachment 234367 [details] smp_rendezvous_action.patch I'm studying `smp_rendezvous` code now. It's a cool feature in the kernel and surprising how long history it has. It seems that arguments of `smp_rendezvous_action` is loaded in local variables as soon as `smp_rendezvous_action` takes a barrier. And the code design seems to use local variables in the barrier. But I think only two lines violate to the design policy and should be fixed as attached `smp_rendezvous_action.patch`. I believe there is no issues about this. `smp_rendezvous` works fine for a long time. I think local variable access is a little bit faster than global variable access. Because the global variables are defined as `volatile`.