Messages in this thread Patch in this message | | | Date | Thu, 3 Jul 2008 21:50:31 +0100 (BST) | From | Hugh Dickins <> | Subject | [PATCH 2.6.26-rc8-mm1] memrlimit: fix mmap_sem deadlock |
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"ps -f" hung after "killall make" of make -j20 kernel builds. It's generally considered bad manners to down_write something you already have down_read. exit_mm up_reads before calling mm_update_next_owner, so I guess exec_mmap can safely do so too. (And with that repositioning there's not much point in mm_need_new_owner allowing for NULL mm.)
Signed-off-by: Hugh Dickins <hugh@veritas.com> --- Fix to memrlimit-cgroup-mm-owner-callback-changes-to-add-task-info.patch quite independent of its recent sleeping-inside-spinlock fix; could even be applied to 2.6.26, though no deadlock there. Gosh, I see those patches have spawned "Reviewed-by" tags in my name: sorry, no, just "Bug-found-by".
fs/exec.c | 2 +- kernel/exit.c | 2 -- 2 files changed, 1 insertion(+), 3 deletions(-)
--- 2.6.26-rc8-mm1/fs/exec.c 2008-07-03 11:35:20.000000000 +0100 +++ linux/fs/exec.c 2008-07-03 20:27:20.000000000 +0100 @@ -738,11 +738,11 @@ static int exec_mmap(struct mm_struct *m tsk->active_mm = mm; activate_mm(active_mm, mm); task_unlock(tsk); - mm_update_next_owner(old_mm); arch_pick_mmap_layout(mm); if (old_mm) { up_read(&old_mm->mmap_sem); BUG_ON(active_mm != old_mm); + mm_update_next_owner(old_mm); mmput(old_mm); return 0; } --- 2.6.26-rc8-mm1/kernel/exit.c 2008-07-03 11:35:37.000000000 +0100 +++ linux/kernel/exit.c 2008-07-03 20:28:35.000000000 +0100 @@ -588,8 +588,6 @@ mm_need_new_owner(struct mm_struct *mm, * If there are other users of the mm and the owner (us) is exiting * we need to find a new owner to take on the responsibility. */ - if (!mm) - return 0; if (atomic_read(&mm->mm_users) <= 1) return 0; if (mm->owner != p)
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