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Groups > linux.kernel > #1643814
| From | David Carrillo-Cisneros <davidcc@google.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] perf/x86/intel/cqm: Make sure the head event of cache_groups always has valid RMID |
| Date | 2017-05-18 07:00 +0200 |
| Message-ID | <tIlHz-4Zo-7@gated-at.bofh.it> (permalink) |
| References | <tDeQp-5Gt-5@gated-at.bofh.it> <tHLXs-6QP-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, May 16, 2017 at 7:38 AM, Peter Zijlstra <peterz@infradead.org> wrote: > On Thu, May 04, 2017 at 10:31:43AM +0800, Zefan Li wrote: >> It is assumed that the head of cache_groups always has valid RMID, >> which isn't true. >> >> When we deallocate RMID from conflicting events currently we don't >> move them to the tail, and one of those events can happen to be in >> the head. Another case is we allocate RMIDs for all the events except >> the head event in intel_cqm_sched_in_event(). >> >> Besides there's another bug that we retry rotating without resetting >> nr_needed and start in __intel_cqm_rmid_rotate(). >> >> Those bugs combined together led to the following oops. >> >> WARNING: at arch/x86/kernel/cpu/perf_event_intel_cqm.c:186 __put_rmid+0x28/0x80() >> ... >> [<ffffffff8103a578>] __put_rmid+0x28/0x80 >> [<ffffffff8103a74a>] intel_cqm_rmid_rotate+0xba/0x440 >> [<ffffffff8109d8cb>] process_one_work+0x17b/0x470 >> [<ffffffff8109e69b>] worker_thread+0x11b/0x400 >> ... >> BUG: unable to handle kernel NULL pointer dereference at (null) I ran into this bug long time ago but never found an easy way to reproduce. Do you have one? >> ... >> [<ffffffff8103a74a>] intel_cqm_rmid_rotate+0xba/0x440 >> [<ffffffff8109d8cb>] process_one_work+0x17b/0x470 >> [<ffffffff8109e69b>] worker_thread+0x11b/0x400 > > I've managed to forgot most if not all of that horror show. Vikas and > David seem to be working on a replacement, but until such a time it > would be good if this thing would not crash the kernel. > > Guys, could you have a look? To me it appears to mostly have the right > shape, but like I said, I forgot most details... The patch LGTM. I ran into this issues before and fixed them in a similar but messier way, then the re-write started ... > >> >> Cc: stable@vger.kernel.org >> Signed-off-by: Zefan Li <lizefan@huawei.com> Acked-by: David Carrillo-Cisneros <davidcc@google.com>
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Re: [PATCH] perf/x86/intel/cqm: Make sure the head event of cache_groups always has valid RMID Peter Zijlstra <peterz@infradead.org> - 2017-05-16 16:50 +0200 Re: [PATCH] perf/x86/intel/cqm: Make sure the head event of cache_groups always has valid RMID David Carrillo-Cisneros <davidcc@google.com> - 2017-05-18 07:00 +0200 Re: [PATCH] perf/x86/intel/cqm: Make sure the head event of cache_groups always has valid RMID Shivappa Vikas <vikas.shivappa@linux.intel.com> - 2017-05-22 19:10 +0200
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