Merge tag 'v4.3-rc1' into locking/core, to refresh the tree

[karo-tx-linux.git] / kernel / kmod.c

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 81c67050c5aaec7258d70c4ad2dbb9f238860f82..da98d0593de24206d68222d787d059a5a2b025a1 100644 (file)
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -45,8 +45,6 @@
 
 extern int max_threads;
 
-static struct workqueue_struct *khelper_wq;
-
 #define CAP_BSET       (void *)1
 #define CAP_PI         (void *)2
 
@@ -225,7 +223,7 @@ static int call_usermodehelper_exec_async(void *data)
        spin_unlock_irq(&current->sighand->siglock);
 
        /*
-        * Our parent is khelper which runs with elevated scheduling
+        * Our parent (unbound workqueue) runs with elevated scheduling
         * priority. Avoid propagating that into the userspace child.
         */
        set_user_nice(current, 0);
@@ -267,14 +265,9 @@ out:
        do_exit(0);
 }
 
-/*
- * Handles UMH_WAIT_PROC. Our parent khelper can't wait for usermodehelper
- * completion without blocking every other pending requests. That's why
- * we use a kernel thread dedicated for that purpose.
- */
-static int call_usermodehelper_exec_sync(void *data)
+/* Handles UMH_WAIT_PROC.  */
+static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
 {
-       struct subprocess_info *sub_info = data;
        pid_t pid;
 
        /* If SIGCLD is ignored sys_wait4 won't populate the status. */
@@ -288,9 +281,9 @@ static int call_usermodehelper_exec_sync(void *data)
                 * Normally it is bogus to call wait4() from in-kernel because
                 * wait4() wants to write the exit code to a userspace address.
                 * But call_usermodehelper_exec_sync() always runs as kernel
-                * thread and put_user() to a kernel address works OK for kernel
-                * threads, due to their having an mm_segment_t which spans the
-                * entire address space.
+                * thread (workqueue) and put_user() to a kernel address works
+                * OK for kernel threads, due to their having an mm_segment_t
+                * which spans the entire address space.
                 *
                 * Thus the __user pointer cast is valid here.
                 */
@@ -305,39 +298,42 @@ static int call_usermodehelper_exec_sync(void *data)
                        sub_info->retval = ret;
        }
 
+       /* Restore default kernel sig handler */
+       kernel_sigaction(SIGCHLD, SIG_IGN);
+
        umh_complete(sub_info);
-       do_exit(0);
 }
 
 /*
- * This function doesn't strictly needs to be called asynchronously. But we
- * need to create the usermodehelper kernel threads from a task that is affine
- * to all CPUs (or nohz housekeeping ones) such that they inherit a widest
- * affinity irrespective of call_usermodehelper() callers with possibly reduced
- * affinity (eg: per-cpu workqueues). We don't want usermodehelper targets to
- * contend any busy CPU.
- * Khelper provides such wide affinity.
+ * We need to create the usermodehelper kernel thread from a task that is affine
+ * to an optimized set of CPUs (or nohz housekeeping ones) such that they
+ * inherit a widest affinity irrespective of call_usermodehelper() callers with
+ * possibly reduced affinity (eg: per-cpu workqueues). We don't want
+ * usermodehelper targets to contend a busy CPU.
+ *
+ * Unbound workqueues provide such wide affinity and allow to block on
+ * UMH_WAIT_PROC requests without blocking pending request (up to some limit).
  *
- * Besides, khelper provides the privilege level that caller might not have to
- * perform the usermodehelper request.
+ * Besides, workqueues provide the privilege level that caller might not have
+ * to perform the usermodehelper request.
  *
  */
 static void call_usermodehelper_exec_work(struct work_struct *work)
 {
        struct subprocess_info *sub_info =
                container_of(work, struct subprocess_info, work);
-       pid_t pid;
 
-       if (sub_info->wait & UMH_WAIT_PROC)
-               pid = kernel_thread(call_usermodehelper_exec_sync, sub_info,
-                                   CLONE_FS | CLONE_FILES | SIGCHLD);
-       else
+       if (sub_info->wait & UMH_WAIT_PROC) {
+               call_usermodehelper_exec_sync(sub_info);
+       } else {
+               pid_t pid;
+
                pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
                                    SIGCHLD);
-
-       if (pid < 0) {
-               sub_info->retval = pid;
-               umh_complete(sub_info);
+               if (pid < 0) {
+                       sub_info->retval = pid;
+                       umh_complete(sub_info);
+               }
        }
 }
 
@@ -549,8 +545,8 @@ EXPORT_SYMBOL(call_usermodehelper_setup);
  *        from interrupt context.
  *
  * Runs a user-space application.  The application is started
- * asynchronously if wait is not set, and runs as a child of khelper.
- * (ie. it runs with full root capabilities and wide affinity).
+ * asynchronously if wait is not set, and runs as a child of system workqueues.
+ * (ie. it runs with full root capabilities and optimized affinity).
  */
 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 {
@@ -562,7 +558,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
                return -EINVAL;
        }
        helper_lock();
-       if (!khelper_wq || usermodehelper_disabled) {
+       if (usermodehelper_disabled) {
                retval = -EBUSY;
                goto out;
        }
@@ -574,7 +570,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
        sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
        sub_info->wait = wait;
 
-       queue_work(khelper_wq, &sub_info->work);
+       queue_work(system_unbound_wq, &sub_info->work);
        if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
                goto unlock;
 
@@ -704,9 +700,3 @@ struct ctl_table usermodehelper_table[] = {
        },
        { }
 };
-
-void __init usermodehelper_init(void)
-{
-       khelper_wq = create_singlethread_workqueue("khelper");
-       BUG_ON(!khelper_wq);
-}