extern int max_threads;
-static struct workqueue_struct *khelper_wq;
-
#define CAP_BSET (void *)1
#define CAP_PI (void *)2
* @...: arguments as specified in the format string
*
* Load a module using the user mode module loader. The function returns
- * zero on success or a negative errno code on failure. Note that a
- * successful module load does not mean the module did not then unload
- * and exit on an error of its own. Callers must check that the service
- * they requested is now available not blindly invoke it.
+ * zero on success or a negative errno code or positive exit code from
+ * "modprobe" on failure. Note that a successful module load does not mean
+ * the module did not then unload and exit on an error of its own. Callers
+ * must check that the service they requested is now available not blindly
+ * invoke it.
*
* If module auto-loading support is disabled then this function
* becomes a no-operation.
/*
* This is the task which runs the usermode application
*/
-static int ____call_usermodehelper(void *data)
+static int call_usermodehelper_exec_async(void *data)
{
struct subprocess_info *sub_info = data;
struct cred *new;
flush_signal_handlers(current, 1);
spin_unlock_irq(¤t->sighand->siglock);
- /* We can run anywhere, unlike our parent keventd(). */
- set_cpus_allowed_ptr(current, cpu_all_mask);
-
/*
- * Our parent is keventd, which runs with elevated scheduling priority.
- * Avoid propagating that into the userspace child.
+ * Our parent (unbound workqueue) runs with elevated scheduling
+ * priority. Avoid propagating that into the userspace child.
*/
set_user_nice(current, 0);
(const char __user *const __user *)sub_info->envp);
out:
sub_info->retval = retval;
- /* wait_for_helper() will call umh_complete if UHM_WAIT_PROC. */
+ /*
+ * call_usermodehelper_exec_sync() will call umh_complete
+ * if UHM_WAIT_PROC.
+ */
if (!(sub_info->wait & UMH_WAIT_PROC))
umh_complete(sub_info);
if (!retval)
do_exit(0);
}
-/* Keventd can't block, but this (a child) can. */
-static int wait_for_helper(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. */
kernel_sigaction(SIGCHLD, SIG_DFL);
- pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
+ pid = kernel_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
if (pid < 0) {
sub_info->retval = pid;
} else {
/*
* Normally it is bogus to call wait4() from in-kernel because
* wait4() wants to write the exit code to a userspace address.
- * But wait_for_helper() always runs as keventd, 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.
+ * But call_usermodehelper_exec_sync() always runs as kernel
+ * 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.
*/
sys_wait4(pid, (int __user *)&ret, 0, NULL);
/*
- * If ret is 0, either ____call_usermodehelper failed and the
- * real error code is already in sub_info->retval or
+ * If ret is 0, either call_usermodehelper_exec_async failed and
+ * the real error code is already in sub_info->retval or
* sub_info->retval is 0 anyway, so don't mess with it then.
*/
if (ret)
sub_info->retval = ret;
}
+ /* Restore default kernel sig handler */
+ kernel_sigaction(SIGCHLD, SIG_IGN);
+
umh_complete(sub_info);
- do_exit(0);
}
-/* This is run by khelper thread */
-static void __call_usermodehelper(struct work_struct *work)
+/*
+ * 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, 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(wait_for_helper, sub_info,
- CLONE_FS | CLONE_FILES | SIGCHLD);
- else
- pid = kernel_thread(____call_usermodehelper, sub_info,
- SIGCHLD);
-
- if (pid < 0) {
- sub_info->retval = pid;
- umh_complete(sub_info);
+ if (sub_info->wait & UMH_WAIT_PROC) {
+ call_usermodehelper_exec_sync(sub_info);
+ } else {
+ pid_t pid;
+ /*
+ * Use CLONE_PARENT to reparent it to kthreadd; we do not
+ * want to pollute current->children, and we need a parent
+ * that always ignores SIGCHLD to ensure auto-reaping.
+ */
+ pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
+ CLONE_PARENT | SIGCHLD);
+ if (pid < 0) {
+ sub_info->retval = pid;
+ umh_complete(sub_info);
+ }
}
}
if (!sub_info)
goto out;
- INIT_WORK(&sub_info->work, __call_usermodehelper);
+ INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
sub_info->path = path;
sub_info->argv = argv;
sub_info->envp = envp;
* from interrupt context.
*
* Runs a user-space application. The application is started
- * asynchronously if wait is not set, and runs as a child of keventd.
- * (ie. it runs with full root capabilities).
+ * 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)
{
return -EINVAL;
}
helper_lock();
- if (!khelper_wq || usermodehelper_disabled) {
+ if (usermodehelper_disabled) {
retval = -EBUSY;
goto out;
}
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;
},
{ }
};
-
-void __init usermodehelper_init(void)
-{
- khelper_wq = create_singlethread_workqueue("khelper");
- BUG_ON(!khelper_wq);
-}
Code Review / kvmfornfv.git / blobdiff