The patch titled
Subject: proc/kcore: don't grab lock for kclist_add()
has been added to the -mm tree. Its filename is
proc-kcore-dont-grab-lock-for-kclist_add.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-kcore-dont-grab-lock-for-kclist_add.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-kcore-dont-grab-lock-for-kclist_add.patch
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------------------------------------------------------
From: Omar Sandoval <osandov@xxxxxx>
Subject: proc/kcore: don't grab lock for kclist_add()
Patch series "/proc/kcore improvements", v2.
This series makes a few improvements to /proc/kcore. Patches 1 and 2 are
prep patches. Patch 3 is a fix/cleanup. Patch 4 is another prep patch.
Patches 5 and 6 are optimizations to ->read(). Patch 7 adds vmcoreinfo to
/proc/kcore (apparently I'm not the only one who wants this, see
https://www.spinics.net/lists/arm-kernel/msg665103.html).
I tested that the crash utility still works with this applied, and readelf
is happy with it, as well.
This patch (of 7):
kclist_add() is only called at init time, so there's no point in grabbing
any locks. We're also going to replace the rwlock with a rwsem, which we
don't want to try grabbing during early boot.
Link: http://lkml.kernel.org/r/ddbe991f42b8d49e50645878ad8c1a8168db2e82.1531440458.git.osandov@xxxxxx
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN fs/proc/kcore.c~proc-kcore-dont-grab-lock-for-kclist_add fs/proc/kcore.c
--- a/fs/proc/kcore.c~proc-kcore-dont-grab-lock-for-kclist_add
+++ a/fs/proc/kcore.c
@@ -62,6 +62,7 @@ static LIST_HEAD(kclist_head);
static DEFINE_RWLOCK(kclist_lock);
static int kcore_need_update = 1;
+/* This doesn't grab kclist_lock, so it should only be used at init time. */
void
kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
{
@@ -69,9 +70,7 @@ kclist_add(struct kcore_list *new, void
new->size = size;
new->type = type;
- write_lock(&kclist_lock);
list_add_tail(&new->list, &kclist_head);
- write_unlock(&kclist_lock);
}
static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
_
Patches currently in -mm which might be from osandov@xxxxxx are
proc-kcore-dont-grab-lock-for-kclist_add.patch
proc-kcore-replace-kclist_lock-rwlock-with-rwsem.patch
proc-kcore-fix-memory-hotplug-vs-multiple-opens-race.patch
proc-kcore-hold-lock-during-read.patch
proc-kcore-clean-up-elf-header-generation.patch
proc-kcore-optimize-multiple-page-reads.patch
proc-kcore-add-vmcoreinfo-note-to-proc-kcore.patch
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