Messages in this thread | | | Date | Tue, 24 Oct 2006 08:53:06 -0400 | From | Neil Horman <> | Subject | Re: [KJ][PATCH] Correct misc_register return code handling in several drivers |
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On Tue, Oct 24, 2006 at 01:34:34PM +1000, Benjamin Herrenschmidt wrote: > On Mon, 2006-10-23 at 13:19 -0400, Neil Horman wrote: > > Hey All- > > Janitor patch to clean up return code handling and exit from failed > > calls to misc_register accross several modules. > > The patch doesn't match the description... What are those INIT_LIST_HEAD > things ? Is this something I've missed or is this a new requirement for > all misc devices ? Can't it be statically initialized instead ? >
The INIT_LIST_HEAD is there to prevent a potential oops on module removal. misc_register, if it fails, leaves miscdevice.list unchanged. That means its next and prev pointers contain NULL or garbage, when both pointers should contain &miscdevice.list. If we don't do that, then there is a chance we will oops on module removal when we do a list_del in misc_deregister on the moudule_exit routine. I could have done this statically, but I thought it looked cleaner to do it with the macro in the code.
Thanks & Regards Neil
> > Thanks & Regards > > Neil > > > > Signed-off-by: Neil Horman <nhorman@tuxdriver.com> > > > > > > drivers/char/mmtimer.c | 29 +++++++++++++++++++++++------ > > drivers/char/tpm/tpm.c | 1 + > > drivers/input/misc/hp_sdc_rtc.c | 6 +++++- > > drivers/macintosh/apm_emu.c | 5 ++++- > > drivers/net/tun.c | 2 ++ > > fs/dlm/user.c | 1 + > > 6 files changed, 36 insertions(+), 8 deletions(-) > > > > > > diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c > > --- a/drivers/char/mmtimer.c > > +++ b/drivers/char/mmtimer.c > > @@ -669,6 +669,7 @@ static struct k_clock sgi_clock = { > > static int __init mmtimer_init(void) > > { > > unsigned i; > > + int err = -1; > > cnodeid_t node, maxn = -1; > > > > if (!ia64_platform_is("sn2")) > > @@ -680,7 +681,7 @@ static int __init mmtimer_init(void) > > if (sn_rtc_cycles_per_second < 100000) { > > printk(KERN_ERR "%s: unable to determine clock frequency\n", > > MMTIMER_NAME); > > - return -1; > > + goto out; > > } > > > > mmtimer_femtoperiod = ((unsigned long)1E15 + sn_rtc_cycles_per_second / > > @@ -689,13 +690,13 @@ static int __init mmtimer_init(void) > > if (request_irq(SGI_MMTIMER_VECTOR, mmtimer_interrupt, IRQF_PERCPU, MMTIMER_NAME, NULL)) { > > printk(KERN_WARNING "%s: unable to allocate interrupt.", > > MMTIMER_NAME); > > - return -1; > > + goto out; > > } > > > > if (misc_register(&mmtimer_miscdev)) { > > printk(KERN_ERR "%s: failed to register device\n", > > MMTIMER_NAME); > > - return -1; > > + goto out1; > > } > > > > /* Get max numbered node, calculate slots needed */ > > @@ -709,16 +710,18 @@ static int __init mmtimer_init(void) > > if (timers == NULL) { > > printk(KERN_ERR "%s: failed to allocate memory for device\n", > > MMTIMER_NAME); > > - return -1; > > + goto out2; > > } > > > > + memset(timers,0,(sizeof(mmtimer_t *)*maxn)); > > + > > /* Allocate mmtimer_t's for each online node */ > > for_each_online_node(node) { > > timers[node] = kmalloc_node(sizeof(mmtimer_t)*NUM_COMPARATORS, GFP_KERNEL, node); > > if (timers[node] == NULL) { > > printk(KERN_ERR "%s: failed to allocate memory for device\n", > > MMTIMER_NAME); > > - return -1; > > + goto out3; > > } > > for (i=0; i< NUM_COMPARATORS; i++) { > > mmtimer_t * base = timers[node] + i; > > @@ -738,7 +741,21 @@ static int __init mmtimer_init(void) > > printk(KERN_INFO "%s: v%s, %ld MHz\n", MMTIMER_DESC, MMTIMER_VERSION, > > sn_rtc_cycles_per_second/(unsigned long)1E6); > > > > - return 0; > > + err = 0; > > +out: > > + return err; > > + > > +out3: > > + for_each_online_node(node) { > > + if(timers[node] != NULL) > > + kfree(timers[node]); > > + } > > +out2: > > + misc_deregister(&mmtimer_miscdev); > > +out1: > > + free_irq(SGI_MMTIMER_VECTOR, NULL); > > + goto out; > > + > > } > > > > module_init(mmtimer_init); > > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c > > --- a/drivers/char/tpm/tpm.c > > +++ b/drivers/char/tpm/tpm.c > > @@ -1155,6 +1155,7 @@ #define DEVNAME_SIZE 7 > > > > if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) { > > list_del(&chip->list); > > + misc_deregister(&chip->vendor.miscdev); > > put_device(dev); > > clear_bit(chip->dev_num, dev_mask); > > kfree(chip); > > diff --git a/drivers/input/misc/hp_sdc_rtc.c b/drivers/input/misc/hp_sdc_rtc.c > > --- a/drivers/input/misc/hp_sdc_rtc.c > > +++ b/drivers/input/misc/hp_sdc_rtc.c > > @@ -693,9 +693,13 @@ static int __init hp_sdc_rtc_init(void) > > > > init_MUTEX(&i8042tregs); > > > > + INIT_LIST_HEAD(&hp_sdc_rtc_dev.list); > > + > > if ((ret = hp_sdc_request_timer_irq(&hp_sdc_rtc_isr))) > > return ret; > > - misc_register(&hp_sdc_rtc_dev); > > + if (misc_register(&hp_sdc_rtc_dev) != 0) > > + printk(KERN_INFO "Could not register misc. dev for sdc\n"); > > + > > create_proc_read_entry ("driver/rtc", 0, NULL, > > hp_sdc_rtc_read_proc, NULL); > > > > diff --git a/drivers/macintosh/apm_emu.c b/drivers/macintosh/apm_emu.c > > --- a/drivers/macintosh/apm_emu.c > > +++ b/drivers/macintosh/apm_emu.c > > @@ -520,6 +520,8 @@ static int __init apm_emu_init(void) > > { > > struct proc_dir_entry *apm_proc; > > > > + INIT_LIST_HEAD(&apm_device.list); > > + > > if (sys_ctrler != SYS_CTRLER_PMU) { > > printk(KERN_INFO "apm_emu: Requires a machine with a PMU.\n"); > > return -ENODEV; > > @@ -529,7 +531,8 @@ static int __init apm_emu_init(void) > > if (apm_proc) > > apm_proc->owner = THIS_MODULE; > > > > - misc_register(&apm_device); > > + if (misc_register(&apm_device) != 0) > > + printk(KERN_INFO "Could not create misc. device for apm\n"); > > > > pmu_register_sleep_notifier(&apm_sleep_notifier); > > > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > > --- a/drivers/net/tun.c > > +++ b/drivers/net/tun.c > > @@ -856,6 +856,8 @@ static int __init tun_init(void) > > printk(KERN_INFO "tun: %s, %s\n", DRV_DESCRIPTION, DRV_VERSION); > > printk(KERN_INFO "tun: %s\n", DRV_COPYRIGHT); > > > > + INIT_LIST_HEAD(&tun_miscdev.list); > > + > > ret = misc_register(&tun_miscdev); > > if (ret) > > printk(KERN_ERR "tun: Can't register misc device %d\n", TUN_MINOR); > > diff --git a/fs/dlm/user.c b/fs/dlm/user.c > > --- a/fs/dlm/user.c > > +++ b/fs/dlm/user.c > > @@ -773,6 +773,7 @@ int dlm_user_init(void) > > ctl_device.name = "dlm-control"; > > ctl_device.fops = &ctl_device_fops; > > ctl_device.minor = MISC_DYNAMIC_MINOR; > > + INIT_LIST_HEAD(&ctl_device.list); > > > > error = misc_register(&ctl_device); > > if (error)
-- /*************************************************** *Neil Horman *Software Engineer *gpg keyid: 1024D / 0x92A74FA1 - http://pgp.mit.edu ***************************************************/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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