From: Konstantin Khlebnikov khlebnikov@yandex-team.ru
[ Upstream commit c46038017fbdcac627b670c9d4176f1d0c2f5fa3 ]
Do not remain stuck forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation.
Replace the only unkillable mmap_sem lock in clear_refs_write().
Link: http://lkml.kernel.org/r/156007493826.3335.5424884725467456239.stgit@buzz Signed-off-by: Konstantin Khlebnikov khlebnikov@yandex-team.ru Reviewed-by: Roman Gushchin guro@fb.com Reviewed-by: Cyrill Gorcunov gorcunov@gmail.com Reviewed-by: Kirill Tkhai ktkhai@virtuozzo.com Acked-by: Michal Hocko mhocko@suse.com Cc: Alexey Dobriyan adobriyan@gmail.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: Matthew Wilcox willy@infradead.org Cc: Michal Koutný mkoutny@suse.com Cc: Oleg Nesterov oleg@redhat.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/task_mmu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 74965e17ffd5..195fbbaf77d4 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1131,7 +1131,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, goto out_mm; }
- down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) { + count = -EINTR; + goto out_mm; + } tlb_gather_mmu(&tlb, mm, 0, -1); if (type == CLEAR_REFS_SOFT_DIRTY) { for (vma = mm->mmap; vma; vma = vma->vm_next) {