Messages in this thread | | | Date | Thu, 07 Feb 2008 12:23:55 +0300 | From | Pavel Emelyanov <> | Subject | Re: [PATCH][USBATM]: convert heavy init dances to kthread API |
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Duncan Sands wrote: > Hi, > >> The problem is that I couldn't find the maintainer for the code >> in drivers/usb/atm/. > > that would be me (though since I haven't used this modem in years I would > be more than happy to hand it off to someone else). > >> Besides, I don't have a proper hardware to test this. > > I will try to find where I put my old modem and test your patch this weekend.
Oh, that would be great :)
>> @@ -1014,11 +1015,7 @@ static int usbatm_do_heavy_init(void *arg) >> struct usbatm_data *instance = arg; >> int ret; >> >> - daemonize(instance->driver->driver_name); >> allow_signal(SIGTERM); >> - instance->thread_pid = current->pid; >> - >> - complete(&instance->thread_started); > > One reason the completion existed to make sure that the thread was not > sent SIGTERM before the above call to allow_signal(SIGTERM). So I think > you have opened up a (tiny) race by deleting it.
Nope. See my answer below :)
>> static int usbatm_heavy_init(struct usbatm_data *instance) >> { >> - int ret = kernel_thread(usbatm_do_heavy_init, instance, CLONE_FS | CLONE_FILES); >> - >> - if (ret < 0) { >> - usb_err(instance, "%s: failed to create kernel_thread (%d)!\n", __func__, ret); > > Please don't delete this message. > >> - return ret; >> - } >> + struct task_struct *t; >> >> - wait_for_completion(&instance->thread_started); >> + t = kthread_create(usbatm_do_heavy_init, instance, >> + instance->driver->driver_name); >> + if (IS_ERR(t)) >> + return PTR_ERR(t); >> >> + instance->thread = t; >> + wake_up_process(t); > > Does the kthread API guarantee that the kthread is not running until you call
It does. That's why the race, you mentioned above is impossible.
> wake_up_process? Because if not then what is to stop the kthread finishing before > this thread does "instance->thread = t", resulting in an attempt to send a signal > to a dead process later on in disconnect? > > Otherwise it looks fine - thanks! > > By the way, the right thing to do is (I think) to replace the thread with a workqueue > and have users of usbatm register a "shut_down" callback rather than using signals: the > disconnect method would call shut_down rathering than trying to kill the thread. That > way all this mucking around with pids etc wouldn't be needed. All users of usbatm would > need to be modified. I managed to convince myself once that they could all be fixed up > in a fairly simple manner thanks to a few tricks and a completion or two, but I don't > recall the details...
Well, that would be also great, since kill_proc will be gone - that's what I'm trying to achieve.
> Best wishes, > > Duncan. >
Thanks, Pavel
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