The patch titled
Subject: usermodehelper: kill the kmod_thread_locker logic
has been added to the -mm tree. Its filename is
usermodehelper-kill-the-kmod_thread_locker-logic.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/usermodehelper-kill-the-kmod_thread_locker-logic.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/usermodehelper-kill-the-kmod_thread_locker-logic.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: usermodehelper: kill the kmod_thread_locker logic
Now that we do not call kernel_thread(CLONE_VFORK) from the worker thread
we can not deadlock if do_execve() in turn triggers another
call_usermodehelper(), we can remove the kmod_thread_locker code.
Note: we should probably kill khelper_wq and simply use one of the global
workqueues, say, system_unbound_wq, this special wq for umh buys nothing
nowadays.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kmod.c | 33 +++------------------------------
1 file changed, 3 insertions(+), 30 deletions(-)
diff -puN kernel/kmod.c~usermodehelper-kill-the-kmod_thread_locker-logic kernel/kmod.c
--- a/kernel/kmod.c~usermodehelper-kill-the-kmod_thread_locker-logic
+++ a/kernel/kmod.c
@@ -47,13 +47,6 @@ extern int max_threads;
static struct workqueue_struct *khelper_wq;
-/*
- * kmod_thread_locker is used for deadlock avoidance. There is no explicit
- * locking to protect this global - it is private to the singleton khelper
- * thread and should only ever be modified by that thread.
- */
-static const struct task_struct *kmod_thread_locker;
-
#define CAP_BSET (void *)1
#define CAP_PI (void *)2
@@ -273,13 +266,6 @@ out:
do_exit(0);
}
-static int call_helper(void *data)
-{
- /* Worker thread started blocking khelper thread. */
- kmod_thread_locker = current;
- return ____call_usermodehelper(data);
-}
-
/* Keventd can't block, but this (a child) can. */
static int wait_for_helper(void *data)
{
@@ -327,11 +313,9 @@ static void __call_usermodehelper(struct
if (sub_info->wait & UMH_WAIT_PROC)
pid = kernel_thread(wait_for_helper, sub_info,
CLONE_FS | CLONE_FILES | SIGCHLD);
- else {
- pid = kernel_thread(call_helper, sub_info, SIGCHLD);
- /* Worker thread stopped blocking khelper thread. */
- kmod_thread_locker = NULL;
- }
+ else
+ pid = kernel_thread(____call_usermodehelper, sub_info,
+ SIGCHLD);
if (pid < 0) {
sub_info->retval = pid;
@@ -565,17 +549,6 @@ int call_usermodehelper_exec(struct subp
goto out;
}
/*
- * Worker thread must not wait for khelper thread at below
- * wait_for_completion() if the thread was created with CLONE_VFORK
- * flag, for khelper thread is already waiting for the thread at
- * wait_for_completion() in do_fork().
- */
- if (wait != UMH_NO_WAIT && current == kmod_thread_locker) {
- retval = -EBUSY;
- goto out;
- }
-
- /*
* Set the completion pointer only if there is a waiter.
* This makes it possible to use umh_complete to free
* the data structure in case of UMH_NO_WAIT.
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
kernel-kmod-fix-use-after-free-of-the-sub_info-structure.patch
kernel-kmod-fix-use-after-free-of-the-sub_info-structure-v2.patch
usermodehelper-dont-use-clone_vfork-for-____call_usermodehelper.patch
usermodehelper-kill-the-kmod_thread_locker-logic.patch
linux-next.patch
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