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proc: use down_read_killable mmap_sem for /proc/pid/maps 

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

This function is also used for /proc/pid/smaps.

Link: http://lkml.kernel.org/r/156007493160.3335.14447544314127417266.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>
alistair/sunxi64-5.4-dsi
Konstantin Khlebnikov 2019-07-11 20:59:50 -07:00 committed by Linus Torvalds
parent cbf800d9c7
commit 8a713e7df3
2 changed files with 10 additions and 2 deletions
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6
fs/proc/task_mmu.c
View File

@ -166,7 +166,11 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
if (!mm || !mmget_not_zero(mm))
return NULL;
down_read(&mm->mmap_sem);
if (down_read_killable(&mm->mmap_sem)) {
mmput(mm);
return ERR_PTR(-EINTR);
}
hold_task_mempolicy(priv);
priv->tail_vma = get_gate_vma(mm);

6
fs/proc/task_nommu.c
View File

@ -211,7 +211,11 @@ static void *m_start(struct seq_file *m, loff_t *pos)
if (!mm || !mmget_not_zero(mm))
return NULL;
down_read(&mm->mmap_sem);
if (down_read_killable(&mm->mmap_sem)) {
mmput(mm);
return ERR_PTR(-EINTR);
}
/* start from the Nth VMA */
for (p = rb_first(&mm->mm_rb); p; p = rb_next(p))
if (n-- == 0)