On Wed, Sep 25, 2013 at 2:34 PM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> On Wed, Sep 25, 2013 at 01:22:08PM -0400, Lidza Louina wrote:
>>
>> I looked at other uses of the function alloc_tty_driver() in
>> the kernel and none of them seem to follow up with a
>> call to kfree().
>
> Read my first response again. I showed how to do this. Your setting
> up a bunch of things in a line. If any of them fail you need to
> cleanup by releasing any allocations.
>
> If you have an allocation from alloc_tty_driver() then you can't release
> it with kfree() you need to use put_tty_driver().
Alrighty.
These are the examples I'd found in the kernel.
Case 1: tty/synclink.c: mgsl_init_tty(): The serial_driver is
allocated, it checks for an error and returns -ENOMEM:
serial_driver = alloc_tty_driver(128);
if (!serial_driver)
return -ENOMEM;
The code doesn't call put_tty_driver until synclink_cleanup() is
called. In synclink, the put_tty_driver only gets called when
serial_driver is not null:
if (serial_driver) {
if ((rc = tty_unregister_driver(serial_driver)))
printk("%s(%d) failed to unregister tty driver err=%d\n",
__FILE__,__LINE__,rc);
put_tty_driver(serial_driver);
}
This is the case for most of the drivers I found, it returns -ENOMEM
when the alloc fails, and calls put_tty_driver when something fails
afterward (like when registering the device fails).
Case 2: tty/rocket.c: rp_init(): rocket_driver is allocated using
alloc_tty_driver, and we return ret:
int ret = -ENOMEM, pci_boards_found, isa_boards_found, i;
rocket_driver = alloc_tty_driver(MAX_RP_PORTS);
if (!rocket_driver)
goto err;
.............(some code).............
err:
return ret;
put_tty_driver() gets called when we can't find an IO region:
if (controller && (!request_region(controller, 4, "Comtrol RocketPort"))) {
printk(KERN_ERR "Unable to reserve IO region for first "
"configured ISA RocketPort controller 0x%lx. "
"Driver exiting\n", controller);
ret = -EBUSY;
goto err_tty;
}
.............(some code).............
err_tty:
put_tty_driver(rocket_driver);
And after setting rocket_driver's flags, termios info, type, subtype,
etc., it tries to register the driver:
ret = tty_register_driver(rocket_driver);
if (ret < 0) {
printk(KERN_ERR "Couldn't install tty RocketPort driver\n");
goto err_controller;
}
.............(some code).............
err_controller:
if (controller)
release_region(controller, 4);
I would think that err_controller would have a call to put_tty_driver.
Also I'd think that err_tty would go with the failed register_driver()
call and the err_controller would math the failed request_region. Bad
names? >_<
Case 3: tty/serial/msm_smd_tty.c: smd_tty_init(): This doesn't have a
matching put_tty_driver after alloc_tty_driver.
Case 4: tty/vt/vt.c: vty_init(): This code allocates the driver, then
calls a panic function:
console_driver = alloc_tty_driver(MAX_NR_CONSOLES);
if (!console_driver)
panic("Couldn't allocate console driver\n");
The code doesn't call put_tty_driver at any time, and I'm not sure
what the panic function does. I grepped thru the tty drivers and
couldn't find a declaration or definition for it.
There are more drivers I didn't look at, but I figured this would be
enough for now.
Out of the 18 drivers I checked:
- Most of them returned -ENOMEM when allocating failed and most used
put_tty_driver when registering, requesting a region, or using kthread
failed (not all)
- One called put_tty_driver when the module_exit function was being
called: tty/hvc/hvc_console.c
- One had no put_tty_driver call after it was allocated
- One had a panic function when it encountered an error and I don't
know what panic() does, but it doesnt seem to call put_tty_driver
I think I was just looking at the bad ones. >_< Do the ones I caught
need fixing? :)
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