Revision a74aa9676c0256eac05efb2c8e3127e0835e66e5 authored by Linus Torvalds on 11 July 2018, 17:10:50 UTC, committed by Linus Torvalds on 11 July 2018, 17:10:50 UTC
Pull char/misc fixes from Greg KH: "Here are a few char/misc driver fixes for 4.18-rc5. The "largest" stuff here is fixes for the UIO changes in 4.18-rc1 that caused breakages for some people. Thanks to Xiubo Li for fixing them quickly. Other than that, minor fixes for thunderbolt, vmw_balloon, nvmem, mei, ibmasm, and mei drivers. There's also a MAINTAINERS update where Rafael is offering to help out with reviewing driver core patches. All of these have been in linux-next with no reported issues" * tag 'char-misc-4.18-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: nvmem: Don't let a NULL cell_id for nvmem_cell_get() crash us thunderbolt: Notify userspace when boot_acl is changed uio: fix crash after the device is unregistered uio: change to use the mutex lock instead of the spin lock uio: use request_threaded_irq instead fpga: altera-cvp: Fix an error handling path in 'altera_cvp_probe()' ibmasm: don't write out of bounds in read handler MAINTAINERS: Add myself as driver core changes reviewer mei: discard messages from not connected client during power down. vmw_balloon: fix inflation with batching
task_work.c
// SPDX-License-Identifier: GPL-2.0
#include <linux/spinlock.h>
#include <linux/task_work.h>
#include <linux/tracehook.h>
static struct callback_head work_exited; /* all we need is ->next == NULL */
/**
* task_work_add - ask the @task to execute @work->func()
* @task: the task which should run the callback
* @work: the callback to run
* @notify: send the notification if true
*
* Queue @work for task_work_run() below and notify the @task if @notify.
* Fails if the @task is exiting/exited and thus it can't process this @work.
* Otherwise @work->func() will be called when the @task returns from kernel
* mode or exits.
*
* This is like the signal handler which runs in kernel mode, but it doesn't
* try to wake up the @task.
*
* Note: there is no ordering guarantee on works queued here.
*
* RETURNS:
* 0 if succeeds or -ESRCH.
*/
int
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
{
struct callback_head *head;
do {
head = READ_ONCE(task->task_works);
if (unlikely(head == &work_exited))
return -ESRCH;
work->next = head;
} while (cmpxchg(&task->task_works, head, work) != head);
if (notify)
set_notify_resume(task);
return 0;
}
/**
* task_work_cancel - cancel a pending work added by task_work_add()
* @task: the task which should execute the work
* @func: identifies the work to remove
*
* Find the last queued pending work with ->func == @func and remove
* it from queue.
*
* RETURNS:
* The found work or NULL if not found.
*/
struct callback_head *
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
struct callback_head **pprev = &task->task_works;
struct callback_head *work;
unsigned long flags;
if (likely(!task->task_works))
return NULL;
/*
* If cmpxchg() fails we continue without updating pprev.
* Either we raced with task_work_add() which added the
* new entry before this work, we will find it again. Or
* we raced with task_work_run(), *pprev == NULL/exited.
*/
raw_spin_lock_irqsave(&task->pi_lock, flags);
while ((work = READ_ONCE(*pprev))) {
if (work->func != func)
pprev = &work->next;
else if (cmpxchg(pprev, work, work->next) == work)
break;
}
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
return work;
}
/**
* task_work_run - execute the works added by task_work_add()
*
* Flush the pending works. Should be used by the core kernel code.
* Called before the task returns to the user-mode or stops, or when
* it exits. In the latter case task_work_add() can no longer add the
* new work after task_work_run() returns.
*/
void task_work_run(void)
{
struct task_struct *task = current;
struct callback_head *work, *head, *next;
for (;;) {
/*
* work->func() can do task_work_add(), do not set
* work_exited unless the list is empty.
*/
raw_spin_lock_irq(&task->pi_lock);
do {
work = READ_ONCE(task->task_works);
head = !work && (task->flags & PF_EXITING) ?
&work_exited : NULL;
} while (cmpxchg(&task->task_works, work, head) != work);
raw_spin_unlock_irq(&task->pi_lock);
if (!work)
break;
do {
next = work->next;
work->func(work);
work = next;
cond_resched();
} while (work);
}
}
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