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Date: Wed, 16 Mar 2016 15:21:24 +0530
From: Chandra Sekhar Lingutla <clingutla@...eaurora.org>
To: Ming Lei <ming.lei@...onical.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-arm-msm@...r.kernel.org,
Russell King <linux@....linux.org.uk>
Subject: Re: Possible race at user mode helper in request_firmware
Hi Ming,
On 03/16/2016 02:34 PM, Chandra Sekhar Lingutla wrote:
> On 03/16/2016 02:28 PM, Ming Lei wrote:
>> On Wed, Mar 16, 2016 at 4:48 PM, Chandra Sekhar Lingutla
>> <clingutla@...eaurora.org> wrote:
>>> On 03/16/2016 02:12 PM, Ming Lei wrote:
>>>>
>>>> On Wed, Mar 16, 2016 at 3:02 PM, Chandra Sekhar Lingutla
>>>> <clingutla@...eaurora.org> wrote:
>>>>>
>>>>> Hi Ming,
>>>>>
>>>>>
>>>>> On 03/16/2016 07:36 AM, Ming Lei wrote:
>>>>>>
>>>>>>
>>>>>> On Tue, Mar 15, 2016 at 11:09 PM, Ming Lei <ming.lei@...onical.com>
>>>>>> wrote:
>>>>>>>
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> On Mon, Mar 14, 2016 at 8:00 PM, <clingutla@...eaurora.org> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> I see possible race in _request_firmware_load function, on which I
>>>>>>>> wanted to
>>>>>>>> take your opinion.
>>>>>>>>
>>>>>>>> When system is going to low power mode, device_cache_fw_images() is
>>>>>>>> called
>>>>>>>> from pm notifier which schedules asynchronous workers to cache devices
>>>>>>>> firmware.
>>>>>>>> If more than 2 async requests falls under user helper mode, then there
>>>>>>>> is a
>>>>>>>> use after free of "firmware" directory kobject.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> If two requests are for getting same firmware image, only one can be
>>>>>>> sent
>>>>>>> out and be completed with user helper, please see
>>>>>>> fw_lookup_and_allocate_buf(),
>>>>>>> so the race shouldn't have been triggered in this case.
>>>>>>>
>>>>>>> So I guess your test must be involved with at least two different
>>>>>>> requests.
>>>>>>>
>>>>>>>>
>>>>>>>> The race will hit, when one asynchronous worker calls device_del()
>>>>>>>> while
>>>>>>>> other asynchronous worker calls get_device_parent() in
>>>>>>>> _request_firmware_load().
>>>>>>>> After loading firmware, first worker calls device_del(), and
>>>>>>>> "firmware"
>>>>>>>> directory ref count is 1, so cleanup_glue_dir() calls kobject_put()
>>>>>>>> with
>>>>>>>> gdp_mutex lock held.
>>>>>>>> Meanwhile, second async worker calls device_add(), and
>>>>>>>> get_device_parent()
>>>>>>>> is still able to find the firmware directory kobject in ksets after
>>>>>>>> getting
>>>>>>>> gdp_mutex.
>>>>>>>> This kobject gets added as parent to the second device kobject.
>>>>>>>> By the time of accessing the parent kobject, its ref count was 0 and
>>>>>>>> prints
>>>>>>>> below warning stack followed by crash.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> The trick here is just that we don't use 'struct device' in
>>>>>>> device_cache_fw_images(),
>>>>>>> then the firmware device's parent is null during calling device_add()
>>>>>>> from
>>>>>>> _request_firmware_load(), but this should be allowed by driver core.
>>>>>>>
>>>>>>> From firmware class view, both device_add()/device_del() is run with
>>>>>>> pair,
>>>>>>> and driver core still complains during get_device_parent(), so
>>>>>>> something
>>>>>>> inside driver core should be be wrong, IMO.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Thinking about the issue further, I believe it is a false positive which
>>>>>> is
>>>>>> caused by CONFIG_DEBUG_KOBJECT_RELEASE, follows the story:
>>>>>>
>>>>>> 1) device_add() path
>>>>>>
>>>>>> get_device_parent()
>>>>>> ......
>>>>>> mutex_lock(&gdp_mutex);
>>>>>>
>>>>>> /* find our class-directory at the parent and
>>>>>> reference
>>>>>> it */
>>>>>> spin_lock(&dev->class->p->glue_dirs.list_lock);
>>>>>> list_for_each_entry(k, &dev->class->p->glue_dirs.list,
>>>>>> entry)
>>>>>> if (k->parent == parent_kobj) {
>>>>>> kobj = kobject_get(k);
>>>>>> break;
>>>>>> }
>>>>>> spin_unlock(&dev->class->p->glue_dirs.list_lock);
>>>>>> if (kobj) {
>>>>>> mutex_unlock(&gdp_mutex);
>>>>>> return kobj;
>>>>>> }
>>>>>> k = class_dir_create_and_add(dev->class, parent_kobj);
>>>>>> mutex_unlock(&gdp_mutex);
>>>>>> ......
>>>>>>
>>>>>> 2) device_del() path
>>>>>>
>>>>>> cleanup_device_parent()
>>>>>> ->cleanup_glue_dir()
>>>>>> ->mutex_lock(&gdp_mutex);
>>>>>> ->kobject_put(glue_dir);
>>>>>> ->kobject_cleanup()
>>>>>> ->kobject_del()
>>>>>> ->kobj_kset_leave()
>>>>>> ->mutex_unlock(&gdp_mutex);
>>>>>>
>>>>>> So gdp_mutex is held wrt. both looking up/adding the parent kobject
>>>>>> and removing the parent kobject. Actually with this lock, both glur_dir
>>>>>> kobject's referece counting and joining/leaving kset are run atomically.
>>>>>>
>>>>>> The race you found is triggered by CONFIG_DEBUG_KOBJECT_RELEASE,
>>>>>> which causes kobject_cleanup() to be run in workqueue context and the
>>>>>> lock of gdp_mutex can't be hold in that situation anymore. That is the
>>>>>> root
>>>>>> cause for your race.
>>>>>>
>>>>>> That also said DEBUG_KOBJECT_RELEASE might cause trouble in
>>>>>> some situations.
>>>>>>
>>>>>> Thanks,
>>>>>> Ming
>>>>>>
>>>>> I agree that, CONFIG_DEBUG_KOBJECT_RELEASE can cause the race, as it
>>>>> delays
>>>>> call to kobject_cleanup() which deletes kobj entry in glue_dir list.
>>>>>
>>>>> I see the race even after disabling CONFIG_DEBUG_KOBJECT_RELEASE.
>>>>>
>>>>> The race is between kobject_put() and kobject_get() for the "firmware"
>>>>> directory.
>>>>>
>>>>> In device_del() path, I see the race after the call of
>>>>> cleanup_device_parent().
>>>>> cleanup_device_parent() calls kobject_put(glue_dir) with gdp_mutex lock
>>>>> holding,
>>>>> So ideally, to call kobject_put/kobject_get(glue_dir) we need to acquire
>>>>> gdp_mutex.
>>>>>
>>>>> but kobject_del(kobj) will not hold the gdp_mutex lock while calling
>>>>> kobject_put(kobj->parent).
>>>>>
>>>>> Here is the race:
>>>>>
>>>>> Consider 2 async works calls request_firmware() for 2 different binaries
>>>>> (fw1.bin, fw2.bin)
>>>>> Async work1 got scheduled first, and it falls in user helper mode so it
>>>>> creates "firmware" dir
>>>>> and then creates "fw1.bin" directory to load data from user.
>>>>> After load completion or timeout, it starts cleanup dir's, meantime async
>>>>> work2 got scheduled and
>>>>> it also falls in user helper mode, and story starts here:
>>>>>
>>>>> PATH1 req fw for "fw1.bin"
>>>>> PATH2
>>>>> req fw for "fw2.bin"
>>>>> _request_firmware_load()
>>>>> device_del(dev1)
>>>>>
>>>>> ->cleanup_device_parent()
>>>>>
>>>>> mutex_lock(&gdp_mutex);
>>>>>
>>>>> _request_firmware_load("fw2.bin")
>>>>> kobject_put(kobj->parent); --> firmware ref ->1
>>>>> ->device_add(dev2)
>>>>> mutex_unlock(&gdp_mutex);
>>>>> ->get_device_parent()
>>>>> ->kobject_del()
>>>>> mutex_lock(&gdp_mutex)
>>>>> kobj_kset_leave(kobj); -->del "fw1.bin" kobj in kset
>>>>> list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry)
>>>>> kobject_put(kobj->parent); /* No lock :)*/
>>>>> if (k->parent == parent_kobj) {
>>>>>
>>>>> ->kref_put() --> firmware ref ->0
>>>>> kobj = kobject_get(k); -> k is "firmware"
>>>>> dir
>>>>> ->kboject_release()
>>>>> break;
>>>>>
>>>>> ->kobject_del()
>>>>> }
>>>>>
>>>>> /*here deletes firmware entry in kset*/
>>>>> mutex_unlock(&gdp_mutex)
>>>>>
>>>>> ->dev2->kobj.parent = kobj -> kobj is released already
>>>>>
>>>>>
>>>>>
>>>>> PATH 1 is started removing the kobject of "fw1.bin" and its parent
>>>>> "firmware"
>>>>> .
>>>>> cleanup_device_parent(dev1) makes firmware ref count to 1, by calling
>>>>> kobject_put(firmware) with gdp_mutex held.
>>>>>
>>>>> and kobject_del(dev1->kobj) will again calls kobject_put(kobj->parent)
>>>>> without holding gdp_mutex.
>>>>>
>>>>> In PATH2, glue_dir is able to find "firmware" kobj, as firmware dir kobj
>>>>> is
>>>>> deleted from the glue_dir list at kboject_release().
>>>>> and it calls kobject_get(firmware), by the time PATH1 calls
>>>>> kobject_release(firmware).
>>>>>
>>>>> So PATH2 got reference of freed firmware kobj and added as parent to
>>>>> "fw2.bin" kobj.
>>>>>
>>>>> I think, here is possible fix for this race:
>>>>>
>>>>> ------------------------8<-------------------------------------
>>>>> Signed-off-by: Lingutla Chandrasekhar <clingutla@...eaurora.org>
>>>>>
>>>>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>>>>> index 5d8b713..47bc082 100644
>>>>> --- a/drivers/base/core.c
>>>>> +++ b/drivers/base/core.c
>>>>> @@ -1224,7 +1224,13 @@ void device_del(struct device *dev)
>>>>> BUS_NOTIFY_REMOVED_DEVICE,
>>>>> dev);
>>>>> kobject_uevent(&dev->kobj, KOBJ_REMOVE);
>>>>> cleanup_device_parent(dev);
>>>>> - kobject_del(&dev->kobj);
>>>>> +
>>>>> + if (dev->kobj.parent->kset == &dev->class->p->glue_dirs) {
>>>>> + mutex_lock(&gdp_mutex);
>>>>> + kobject_del(&dev->kobj);
>>>>> + mutex_unlock(&gdp_mutex);
>>>>> + } else
>>>>> + kobject_del(&dev->kobj);
>>>>> put_device(parent);
>>>>> }
>>>>> EXPORT_SYMBOL_GPL(device_del);
>>>>>
>>>>> --------------------------->8-----------------------------------
>>>>
>>>>
>>>> OK, one simpler way is to move cleanup_device_parent(dev)
>>>> after kobject_del(&dev->kobj), which looks more clean too.
>>>>
>>> No, We can't move that, bcz kobject_del(&dev->kobj) will clear the parent.
>>
>> Yeah, but I think it is better to do that and just call
>> cleanup_glue_dir() directly
>> because cleanup_device_parent() should have released the glue_dir.
>>
Sorry, i am not able understand correctly, If we reorder kobje_del and cleanup_device_parent(),
kobject_del() clears kobj->parent, and cleanup_device_parent() gets glue_dir with dev->kobj->parent(),
cleanup_glue_dir() returns without calling kobject_put() as glue_dir is NULL, so firmware dir becomes dangling kobj.
Am I missing something here?
>> BTW, failure path of device_add() has been broken already.
>>
> Yah, forgot to mention that. we need to reorder like above fix, can we?.
>
>>>
>>>
>>>>>
>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> [21147.455038] ------------[ cut here ]------------
>>>>>>>> [21147.458910] WARNING: at <...>/kernel/include/linux/kref.h:47
>>>>>>>> kobject_get+0x50/0x68()
>>>>>>>> [21147.481199] Modules linked in: core_ctl(PO) qdrbg_module(O)
>>>>>>>> qcrypto_module(O)
>>>>>>>> [21147.481256] CPU: 2 PID: 23935 Comm: kworker/u16:8 Tainted: P W O
>>>>>>>> 3.10.84-g0957845-00427-g56a05c2 #1
>>>>>>>> [21147.481284] Workqueue: events_unbound async_run_entry_fn
>>>>>>>> [21147.481296] Call trace:
>>>>>>>> [21147.481315] [<ffffffc000206b60>] dump_backtrace+0x0/0x270
>>>>>>>> [21147.481331] [<ffffffc000206de0>] show_stack+0x10/0x1c
>>>>>>>> [21147.481353] [<ffffffc000d569ec>] dump_stack+0x1c/0x28
>>>>>>>> [21147.481370] [<ffffffc00021cc18>] warn_slowpath_common+0x74/0x9c
>>>>>>>> [21147.481383] [<ffffffc00021ce4c>] warn_slowpath_null+0x14/0x20
>>>>>>>> [21147.481397] [<ffffffc000456b10>] kobject_get+0x4c/0x68
>>>>>>>> [21147.481416] [<ffffffc000609f64>] get_device_parent+0xa0/0x194
>>>>>>>> [21147.481430] [<ffffffc00060a3f4>] device_add+0x100/0x600
>>>>>>>> [21147.481446] [<ffffffc00061c390>] _request_firmware+0x8b4/0xa80
>>>>>>>> [21147.481459] [<ffffffc00061c58c>] request_firmware+0x30/0x3c
>>>>>>>> [21147.481473] [<ffffffc00061c5ec>] cache_firmware+0x54/0xb0
>>>>>>>> [21147.481490] [<ffffffc00061c65c>]
>>>>>>>> __async_dev_cache_fw_image+0x14/0x54
>>>>>>>> [21147.481505] [<ffffffc000243794>] async_run_entry_fn+0x6c/0x12c
>>>>>>>> [21147.481521] [<ffffffc000237e88>] process_one_work+0x264/0x3dc
>>>>>>>> [21147.481535] [<ffffffc0002392c0>] worker_thread+0x1f0/0x340
>>>>>>>> [21147.481553] [<ffffffc00023e500>] kthread+0xac/0xb8
>>>>>>>> [21147.481563] ---[ end trace dabc98ea48b8ba59 ]---
>>>>>>>>
>>>>>>>> [21147.486436] Unable to handle kernel paging request at virtual
>>>>>>>> address
>>>>>>>> 0x6b6b6b6b6b6b6bcb
>>>>>>>> [21147.493816] pgd = ffffffc0a982d000
>>>>>>>> [21147.498337] [6b6b6b6b6b6b6bcb] *pgd=0000000000000000
>>>>>>>> [21147.502287] Internal error: Oops: 96000004 [#1] PREEMPT SMP
>>>>>>>> [21147.507826] Modules linked in: core_ctl(PO) qdrbg_module(O)
>>>>>>>> qcrypto_module(O)
>>>>>>>> [21147.514951] CPU: 2 PID: 23935 Comm: kworker/u16:8 Tainted: P W O
>>>>>>>> 3.10.84-g0957845-00427-g56a05c2 #1
>>>>>>>> [21147.524686] Workqueue: events_unbound async_run_entry_fn
>>>>>>>> [21147.529965] task: ffffffc008138000 ti: ffffffc007880000 task.ti:
>>>>>>>> ffffffc007880000
>>>>>>>> [21147.537438] PC is at sysfs_create_dir+0x34/0xd4
>>>>>>>> [21147.541949] LR is at kobject_add_internal+0x120/0x24c
>>>>>>>> [21147.546979] pc : [<ffffffc000361fa8>] lr : [<ffffffc000456f5c>]
>>>>>>>> pstate:
>>>>>>>> 80000145
>>>>>>>> [21147.996295] Process kworker/u16:8 (pid: 23935, stack limit =
>>>>>>>> 0xffffffc007880058)
>>>>>>>> [21148.003673] Call trace:
>>>>>>>> [21148.006117] [<ffffffc000361fa8>] sysfs_create_dir+0x34/0xd4
>>>>>>>> [21148.011663] [<ffffffc000456f58>] kobject_add_internal+0x11c/0x24c
>>>>>>>> [21148.017737] [<ffffffc0004573ec>] kobject_add+0xc8/0xe4
>>>>>>>> [21148.022863] [<ffffffc00060a410>] device_add+0x11c/0x600
>>>>>>>> [21148.028069] [<ffffffc00061c390>] _request_firmware+0x8b4/0xa80
>>>>>>>> [21148.033886] [<ffffffc00061c58c>] request_firmware+0x30/0x3c
>>>>>>>> [21148.039439] [<ffffffc00061c5ec>] cache_firmware+0x54/0xb0
>>>>>>>> [21148.044822] [<ffffffc00061c65c>]
>>>>>>>> __async_dev_cache_fw_image+0x14/0x54
>>>>>>>> [21148.051249] [<ffffffc000243794>] async_run_entry_fn+0x6c/0x12c
>>>>>>>> [21148.057064] [<ffffffc000237e88>] process_one_work+0x264/0x3dc
>>>>>>>> [21148.062792] [<ffffffc0002392c0>] worker_thread+0x1f0/0x340
>>>>>>>> [21148.068263] [<ffffffc00023e500>] kthread+0xac/0xb8
>>>>>>>> [21148.073039] Code: b5000094 14000026 d000ac54 9125a294 (7940c281)
>>>>>>>> [21148.080312] ---[ end trace dabc98ea48b8ba5a ]---
>>>>>>>>
>>>>>>>> Below is the callstack where the parent is freed from the slub_debug
>>>>>>>> info.
>>>>>>>> 0xFFFFFFC000608D74 \\vmlinux\base/core\class_dir_release+0x0C
>>>>>>>> 0xFFFFFFC0002FE6BC \\vmlinux\slub\free_debug_processing\fail+0x114
>>>>>>>> 0xFFFFFFC0002FE7A0 \\vmlinux\slub\__slab_free+0x44
>>>>>>>> 0xFFFFFFC0002FEE60 \\vmlinux\slub\kfree+0x1F8
>>>>>>>> 0xFFFFFFC000608D70 \\vmlinux\base/core\class_dir_release+0x8
>>>>>>>> 0xFFFFFFC000456D70 \\vmlinux\kobject\kobject_release+0x134
>>>>>>>> 0xFFFFFFC000456E10 \\vmlinux\kobject\kobject_put+0x58
>>>>>>>> 0xFFFFFFC000456C28 \\vmlinux\kobject\kobject_del+0x64
>>>>>>>> 0xFFFFFFC000609D78 \\vmlinux\base/core\device_del+0x150
>>>>>>>> 0xFFFFFFC00061C524
>>>>>>>> \\vmlinux\firmware_class\_request_firmware\out+0x71C
>>>>>>>> 0xFFFFFFC00061C58C \\vmlinux\firmware_class\request_firmware+0x30
>>>>>>>> 0xFFFFFFC00061C5EC \\vmlinux\firmware_class\cache_firmware+0x54
>>>>>>>> 0xFFFFFFC00061C65C
>>>>>>>> \\vmlinux\firmware_class\__async_dev_cache_fw_image+0x14
>>>>>>>> 0xFFFFFFC000243794 \\vmlinux\async\async_run_entry_fn+0x6C
>>>>>>>> 0xFFFFFFC000237E88 \\vmlinux\workqueue\process_one_work+0x264
>>>>>>>> 0xFFFFFFC0002392C0 \\vmlinux\workqueue\worker_thread\recheck+0x1A0
>>>>>>>> 0xFFFFFFC00023E500 \\vmlinux\kthread\kthread+0xAC
>>>>>>>>
>>>>>>>> For similar type of issue, I see there is an existing fix: "sysfs:
>>>>>>>> driver
>>>>>>>> core: Fix glue dir race condition by gdp_mutex".
>>>>>>>>
>>>>>>>>
>>>>>>>> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/base/core.c?id=e4a60d139060975eb956717e4f63ae348d4d8cc5
>>>>>>>>
>>>>>>>> Still I am able to reproduce the issue. I have verified this race on
>>>>>>>> kernels: 3.10, 3.18 and 4.4.
>>>>>>>>
>>>>>>>> I followed below procedure to reproduce the issue:
>>>>>>>> 1. Enable "CONFIG_DEBUG_KOBJECT_RELEASE"
>>>>>>>> 2. Use test_firmware, modified the test for async calls
>>>>>>>> 3. Replace WARN_ON with BUG_ON in kref_get().
>>>>>>>> I ran below script from shell:
>>>>>>>> count=0
>>>>>>>> while [ 1 ]
>>>>>>>> do
>>>>>>>> echo 3 >
>>>>>>>> /sys/devices/virtual/misc/test_firmware/trigger_ufw
>>>>>>>> if [ $? -ne 0 ]; then
>>>>>>>> print "Exiting.. "
>>>>>>>> exit 1
>>>>>>>> fi
>>>>>>>> count=$(($count +1))
>>>>>>>> echo "count $count"
>>>>>>>> done
>>>>>>>>
>>>>>>>> With below patch, I could reproduce the issue in the 2nd iteration.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> I will run your test script to see if there is new findings.
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> -------------------------8<----------------------------------------------
>>>>>>>>
>>>>>>>> To reproduce the race condition, use firmware test and
>>>>>>>> CONFIG_DEBUG_KOBJECT_RELEASE=y, which delays kobject
>>>>>>>> releases. So that we can catch the bug easily.
>>>>>>>>
>>>>>>>> Enabled below flags in kernel config file:
>>>>>>>>
>>>>>>>> +CONFIG_DEBUG_KOBJECT_RELEASE=y
>>>>>>>> +CONFIG_TEST_FIRMWARE=y
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Looks I can't reproduce the issue with your approach.
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> diff --git a/include/linux/kref.h b/include/linux/kref.h
>>>>>>>> index 484604d..727fb24 100644
>>>>>>>> --- a/include/linux/kref.h
>>>>>>>> +++ b/include/linux/kref.h
>>>>>>>> @@ -44,7 +44,7 @@ static inline void kref_get(struct kref *kref)
>>>>>>>> * condition when this kref is freeing by some other thread
>>>>>>>> right
>>>>>>>> now.
>>>>>>>> * In this case one should use kref_get_unless_zero()
>>>>>>>> */
>>>>>>>> - WARN_ON_ONCE(atomic_inc_return(&kref->refcount) < 2);
>>>>>>>> + BUG_ON(atomic_inc_return(&kref->refcount) < 2);
>>>>>>>> }
>>>>>>>>
>>>>>>>> /**
>>>>>>>> diff --git a/lib/test_firmware.c b/lib/test_firmware.c
>>>>>>>> old mode 100644
>>>>>>>> new mode 100755
>>>>>>>> index 86374c1..14c9598
>>>>>>>> --- a/lib/test_firmware.c
>>>>>>>> +++ b/lib/test_firmware.c
>>>>>>>> @@ -18,6 +18,7 @@
>>>>>>>> #include <linux/miscdevice.h>
>>>>>>>> #include <linux/slab.h>
>>>>>>>> #include <linux/uaccess.h>
>>>>>>>> +#include <linux/async.h>
>>>>>>>>
>>>>>>>> +
>>>>>>>> +static ASYNC_DOMAIN_EXCLUSIVE(ufw_domain);
>>>>>>>> +
>>>>>>>> +static void __async_ufw_work(void *name,
>>>>>>>> + async_cookie_t cookie)
>>>>>>>> +{
>>>>>>>> + const struct firmware *fw;
>>>>>>>> + const char *fw_name = name;
>>>>>>>> + int ret;
>>>>>>>> +
>>>>>>>> + pr_err("requesting %s\n", fw_name);
>>>>>>>> +
>>>>>>>> + ret = request_firmware(&fw, fw_name, NULL);
>>>>>>>> + pr_err("loaded: %zu\n", fw ? fw->size : 0);
>>>>>>>> + if (!ret)
>>>>>>>> + kfree(fw);
>>>>>>>> +
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static char *name[] = { "fw1.bin", "fw2.bin"};
>>>>>>>> +
>>>>>>>> +static ssize_t trigger_ufw_store(struct device *dev,
>>>>>>>> + struct device_attribute *attr,
>>>>>>>> + const char *buf, size_t count)
>>>>>>>> +{
>>>>>>>> + int rc, i, c=0;
>>>>>>>> + u32 start;
>>>>>>>> + char *fw_name;
>>>>>>>> +
>>>>>>>> + rc = kstrtou32(buf, 0, &start);
>>>>>>>> + if (rc){
>>>>>>>> + pr_err("Invalid option\n");
>>>>>>>> + return rc;
>>>>>>>> + }
>>>>>>>> + pr_err(" no of iterations %d\n", start);
>>>>>>>> +
>>>>>>>> + for (i=0; i< start; i++)
>>>>>>>> + {
>>>>>>>> + if (c >= 2)
>>>>>>>> + c = 0;
>>>>>>>> + fw_name = name[c++];
>>>>>>>> + async_schedule_domain(__async_ufw_work, (void *)fw_name,
>>>>>>>> &ufw_domain);
>>>>>>>> + }
>>>>>>>> + async_synchronize_full_domain(&ufw_domain);
>>>>>>>> + return count;
>>>>>>>> +}
>>>>>>>>
>>>>>>>> static DEVICE_ATTR_WO(trigger_request);
>>>>>>>> +static DEVICE_ATTR_WO(trigger_ufw);
>>>>>>>>
>>>>>>>> static int __init test_firmware_init(void)
>>>>>>>> {
>>>>>>>> @@ -92,6 +140,12 @@ static int __init test_firmware_init(void)
>>>>>>>> goto dereg;
>>>>>>>> }
>>>>>>>>
>>>>>>>> + rc = device_create_file(test_fw_misc_device.this_device,
>>>>>>>> + &dev_attr_trigger_ufw);
>>>>>>>> + if (rc) {
>>>>>>>> + pr_err("could not create sysfs interface: %d\n", rc);
>>>>>>>> + goto dereg;
>>>>>>>> + }
>>>>>>>> pr_warn("interface ready\n");
>>>>>>>>
>>>>>>>> return 0;
>>>>>>>> @@ -106,7 +160,9 @@ static void __exit test_firmware_exit(void)
>>>>>>>> {
>>>>>>>> release_firmware(test_firmware);
>>>>>>>> device_remove_file(test_fw_misc_device.this_device,
>>>>>>>> - &dev_attr_trigger_request);
>>>>>>>> + &dev_attr_trigger_request);
>>>>>>>> + device_remove_file(test_fw_misc_device.this_device,
>>>>>>>> + &dev_attr_trigger_ufw);
>>>>>>>> misc_deregister(&test_fw_misc_device);
>>>>>>>> pr_warn("removed interface\n");
>>>>>>>> }
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> ----------------------------8<--------------------------------------------
>>>>>>>>
>>>>>>>> Thanks and regards,
>>>>>>>> Chandrasekhar L.
>>>>>>>> --
>>>>>>>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
>>>>>>>> member of
>>>>>>>> Code Aurora Forum,
>>>>>>>> a Linux Foundation Collaborative Project.
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