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Groups > linux.kernel > #1311359
| From | Vlastimil Babka <vbabka@suse.cz> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition |
| Date | 2016-01-18 09:00 +0100 |
| Message-ID | <qScTf-5Ya-1@gated-at.bofh.it> (permalink) |
| References | <qSaRs-4GI-5@gated-at.bofh.it> <qSbDQ-5ho-5@gated-at.bofh.it> <qSbXc-5nZ-3@gated-at.bofh.it> <qSc6R-5GF-7@gated-at.bofh.it> <qSczT-5RA-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 18.1.2016 8:39, Sergey Senozhatsky wrote: > On (01/18/16 16:11), Minchan Kim wrote: > [..] >>> so, even if clear_bit_unlock/test_and_set_bit_lock do smp_mb or >>> barrier(), there is no corresponding barrier from record_obj()->WRITE_ONCE(). >>> so I don't think WRITE_ONCE() will help the compiler, or am I missing >>> something? >> >> We need two things >> 2. memory barrier. >> >> As compiler barrier, WRITE_ONCE works to prevent store tearing here >> by compiler. >> However, if we omit unpin_tag here, we lose memory barrier(e,g, smp_mb) >> so another CPU could see stale data caused CPU memory reordering. > > oh... good find! lost release semantic of unpin_tag()... Ah, release semantic, good point indeed. OK then we need the v2 approach again, with WRITE_ONCE() in record_obj(). Or some kind of record_obj_release() with release semantic, which would be a bit more effective, but I guess migration is not that critical path to be worth introducing it. Thanks, Vlastimil > > -ss >
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[PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Junil Lee <junil0814.lee@lge.com> - 2016-01-18 06:50 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-18 07:20 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Minchan Kim <minchan@kernel.org> - 2016-01-18 07:40 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-18 08:00 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Minchan Kim <minchan@kernel.org> - 2016-01-18 08:10 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-18 08:40 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Vlastimil Babka <vbabka@suse.cz> - 2016-01-18 09:00 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Minchan Kim <minchan@kernel.org> - 2016-01-18 09:20 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-01-18 12:10 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Vlastimil Babka <vbabka@suse.cz> - 2016-01-18 13:20 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Minchan Kim <minchan@kernel.org> - 2016-01-18 15:10 +0100
Re: [PATCH v3] zsmalloc: fix migrate_zspage-zs_free race condition Vlastimil Babka <vbabka@suse.cz> - 2016-01-18 15:20 +0100
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