Messages in this thread Patch in this message | | | Subject | [PATCH] Hugetlb: stop race when reading proc meminfo | From | Eric Paris <> | Date | Thu, 19 Jun 2008 14:15:42 -0400 |
| |
minor nit that hugetlb_report_{,node_}meminfo() does not lock the reading of nr_huge_pages, free_huge_pages, and friends so this is not an atomic set of information put into the buffer. If /proc/meminfo is read while the number of hugetlb pages is in flux it is possible to get incorrect output such as:
HugePages_Total: 7 HugePages_Free: 8 HugePages_Rsvd: 0 Hugepagesize: 4096 kB
(test available at https://bugzilla.redhat.com/attachment.cgi?id=309864)
With the patch we beat on a number of boxes for hours with the above test and saw no inconsistencies in the meminfo output.
Signed-off-by: Eric Paris <eparis@redhat.com>
---
mm/hugetlb.c | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ab17127..fe074d1 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -687,7 +687,9 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write, int hugetlb_report_meminfo(char *buf) { - return sprintf(buf, + int ret; + spin_lock(&hugetlb_lock); + ret = sprintf(buf, "HugePages_Total: %5lu\n" "HugePages_Free: %5lu\n" "HugePages_Rsvd: %5lu\n" @@ -698,17 +700,23 @@ int hugetlb_report_meminfo(char *buf) resv_huge_pages, surplus_huge_pages, HPAGE_SIZE/1024); + spin_unlock(&hugetlb_lock); + return ret; } int hugetlb_report_node_meminfo(int nid, char *buf) { - return sprintf(buf, + int ret; + spin_lock(&hugetlb_lock); + ret = sprintf(buf, "Node %d HugePages_Total: %5u\n" "Node %d HugePages_Free: %5u\n" "Node %d HugePages_Surp: %5u\n", nid, nr_huge_pages_node[nid], nid, free_huge_pages_node[nid], nid, surplus_huge_pages_node[nid]); + spin_unlock(&hugetlb_lock); + return ret; } /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
| |