Messages in this thread | | | Date | Wed, 5 Nov 2014 10:01:39 +0800 | From | Yijing Wang <> | Subject | Re: Subject: [PATCH] kobject: fix the race between kobject_del and get_device_parent |
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On 2014/11/5 3:15, Tejun Heo wrote: > Hello, > > Sorry about the delay.
Thank you for your review and comments.
> > On Wed, Oct 22, 2014 at 04:07:44PM +0800, Weng Meiling wrote: >> diff --git a/drivers/base/core.c b/drivers/base/core.c >> index 28b808c..645eacf 100644 >> --- a/drivers/base/core.c >> +++ b/drivers/base/core.c >> @@ -724,12 +724,12 @@ class_dir_create_and_add(struct class *class, struct kobject *parent_kobj) >> return &dir->kobj; >> } >> >> +static DEFINE_MUTEX(gdp_mutex); >> >> static struct kobject *get_device_parent(struct device *dev, >> struct device *parent) >> { >> if (dev->class) { >> - static DEFINE_MUTEX(gdp_mutex); >> struct kobject *kobj = NULL; >> struct kobject *parent_kobj; >> struct kobject *k; >> @@ -793,7 +793,9 @@ static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir) >> glue_dir->kset != &dev->class->p->glue_dirs) >> return; >> >> + mutex_lock(&gdp_mutex); >> kobject_put(glue_dir); >> + mutex_unlock(&gdp_mutex); > > So, yeah, this looks like a correct approach; however, do we even need > to clear the glue directories?
Yes. In our platform, the glue directories /sys/devices/virtual/block will be removed once the last child device call device_del().
> What's the downside of just keeping > them around once created?
Without the fix, kernel will report the bug as bellow:
We tested it in 3.4 kernel, but this issue still exists in latest kernel.
<2>[ 3965.441912] kernel BUG at /usr/src/packages/BUILD/kernel-default-3.4.24.19/linux-3.4/fs/sysfs/group.c:65! <4>[ 3965.441915] invalid opcode: 0000 [#1] SMP <4>[ 3965.443707] calling kbox_sync :begin <4>[ 3965.447262] sync kbox :begin <4>[ 3965.450122] open all redirect device :begin <4>[ 3965.454276] open all redirect device :end <4>[ 3965.458257] flush kbox regions :begin <4>[ 3965.461897] kbox region (die) is writing into (biosnvram), action is 202 <4>[ 3965.468556] test write len : 2009 <4>[ 3965.471847] first start addr : ffff88007e706000 ...... <4>[ 3965.686743] [<ffffffff811a677e>] sysfs_create_group+0xe/0x10 <4>[ 3965.686748] [<ffffffff810cfb04>] blk_trace_init_sysfs+0x14/0x20 <4>[ 3965.686753] [<ffffffff811fcabb>] blk_register_queue+0x3b/0x120 <4>[ 3965.686756] [<ffffffff812030bc>] add_disk+0x1cc/0x490 <4>[ 3965.686770] [<ffffffffa36a67c6>] SDM_BLKAddBlkDisk+0x86/0x290 [sdm] <4>[ 3965.686780] [<ffffffffa36a6a55>] SDM_BLKRegisterThread+0x85/0x330 [sdm] <4>[ 3965.686801] [<ffffffffa00dfb7e>] LVOS_SchedWorkThread+0xde/0x190 [vos] <4>[ 3965.686806] [<ffffffff8144a8a4>] kernel_thread_helper+0x4/0x10 <4>[ 3965.686821] [<ffffffffa00dfaa0>] ? LVOS_CreateSchedWorkThread+0xd0/0xd0 [vos] <4>[ 3965.686825] [<ffffffff8144a8a0>] ? gs_change+0x13/0x13
Hi Tejun, if you think it make sense, I will resend it to make Greg easy review and apply.
Thanks! Yijing.
> > Thanks. >
-- Thanks! Yijing
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