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author | Arun KS <arunks@codeaurora.org> | 2018-12-28 00:34:20 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-28 12:11:47 -0800 |
commit | 3d6357de8aa09e1966770dc1171c72679946464f (patch) | |
tree | a24bb2f8795ea4927c1ff64d5f5f00398bee925d /arch/x86/kernel | |
parent | fecd4a50baaebf6bde7f9e0b88fef13ffe5d98a1 (diff) | |
download | linux-3d6357de8aa09e1966770dc1171c72679946464f.tar.gz |
mm: reference totalram_pages and managed_pages once per function
Patch series "mm: convert totalram_pages, totalhigh_pages and managed pages to atomic", v5. This series converts totalram_pages, totalhigh_pages and zone->managed_pages to atomic variables. totalram_pages, zone->managed_pages and totalhigh_pages updates are protected by managed_page_count_lock, but readers never care about it. Convert these variables to atomic to avoid readers potentially seeing a store tear. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better to remove the lock and convert variables to atomic. With the change, preventing poteintial store-to-read tearing comes as a bonus. This patch (of 4): This is in preparation to a later patch which converts totalram_pages and zone->managed_pages to atomic variables. Please note that re-reading the value might lead to a different value and as such it could lead to unexpected behavior. There are no known bugs as a result of the current code but it is better to prevent from them in principle. Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.org Signed-off-by: Arun KS <arunks@codeaurora.org> Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r-- | arch/x86/kernel/cpu/microcode/core.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 2637ff09d6a0..168fa272cc3e 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -434,9 +434,10 @@ static ssize_t microcode_write(struct file *file, const char __user *buf, size_t len, loff_t *ppos) { ssize_t ret = -EINVAL; + unsigned long nr_pages = totalram_pages; - if ((len >> PAGE_SHIFT) > totalram_pages) { - pr_err("too much data (max %ld pages)\n", totalram_pages); + if ((len >> PAGE_SHIFT) > nr_pages) { + pr_err("too much data (max %ld pages)\n", nr_pages); return ret; } |