The list of transaction is enumerated without acquiring card lock when
processing AR response event. This causes a race condition bug when
processing AT request completion event concurrently.
This commit fixes the bug by put timer start for split transaction
expiration into the scope of lock. The value of jiffies in card structure
is referred before acquiring the lock.
Cc: stable@vger.kernel.org # v6.18
Fixes: b5725cfa41 ("firewire: core: use spin lock specific to timer for split transaction")
Reported-by: Andreas Persson <andreasp56@outlook.com>
Closes: https://github.com/alsa-project/snd-firewire-ctl-services/issues/209
Tested-by: Andreas Persson <andreasp56@outlook.com>
Link: https://lore.kernel.org/r/20260127223413.22265-1-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
This release includes two changes for core functions, which affects all
use cases of this subsystem.
- Handle per-device interoperability quirks
It is well known that some devices have quirks affecting
interoperability. To identify such quirks at an early stages of
device detection, the step for reading the configuration ROM contents
has been changed. As a side effect, the entire detection process is
now performed at the basic transaction speed (S100), without no trial
to probe higher supported speeds.
With this change, the following devices should now work with fewer
issues:
- TASCAM FW-1884, FW-1804, and FW-1082
- MOTU Audio Express
- Safer removals of host card
There was a race condition between host card removal and handling of
bus reset events in the workqueue. This appears to be a long standing
issue (for a dozen years or so[1]), and recent changes to use more
workqueues escalate it. To solve it, a new callback has been added to
the 1394 OHCI PCI driver to unregister the interrupt sources and wait
for workqueue completions when removing a card instance.
[1] https://sourceforge.net/p/linux1394/mailman/linux1394-devel/thread/20250629024836.GA16759%40workstation.local/#msg59200628
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Merge tag 'firewire-updates-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394
Pull firewire updates from Takashi Sakamoto:
"This includes two changes for core functions, which affects all use
cases of this subsystem:
- Handle per-device interoperability quirks
Some devices have quirks affecting interoperability. To identify
such quirks at an early stages of device detection, the step for
reading the configuration ROM contents has been changed. As a side
effect, the entire detection process is now performed at the basic
transaction speed (S100), without a trial to probe higher
supported speeds.
With this change, the following devices should now work with fewer
issues:
- TASCAM FW-1884, FW-1804, and FW-1082
- MOTU Audio Express
- Safer removals of host card
There was a race condition between host card removal and handling
of bus reset events in the workqueue. This appears to be a long
standing issue, and recent changes to use more workqueues escalate
it.
To solve it, a new callback has been added to the 1394 OHCI PCI
driver to unregister the interrupt sources and wait for workqueue
completions when removing a card instance"
* tag 'firewire-updates-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394:
firewire: core: abort pending transactions at card removal
firewire: core: add WQ_UNBOUND to alloc_workqueue users
firewire: core: clear sources of hardware interrupt at card removal
firewire: core: code refactoring to find and pop transaction entry
firewire: core: code refactoring to remove transaction entry
firewire: core: use cleanup function to release cached configuration ROM
ALSA: firewire-tascam: reserve resources for transferred isochronous packets at S400
firewire: core: handle device quirk of TASCAM FW-1884/FW-1804/FW-1082
firewire: core: determine transaction speed after detecting quirks
firewire: core: code refactoring to compute transaction speed
firewire: core: handle device quirk of MOTU Audio Express
firewire: core: detect device quirk when reading configuration ROM
IEEE 1394 defines the split, concatenated, and unified transaction.
To support the split transaction, core function uses linked list to
maintain the transactions waiting for acknowledge packet. After clearing
sources of hardware interrupts, the acknowledge packet is no longer
handled, therefore it is required to abort the pending transactions.
This commit executes callback with RCODE_CANCELLED for the pending
transactions at card removal.
Link: https://lore.kernel.org/r/20251111223834.311287-1-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Currently if a user enqueues a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistency cannot be addressed without refactoring the API.
alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.
This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.
This continues the effort to refactor workqueue APIs, which began with
the introduction of new workqueues and a new alloc_workqueue flag in:
commit 128ea9f6cc ("workqueue: Add system_percpu_wq and system_dfl_wq")
commit 930c2ea566 ("workqueue: Add new WQ_PERCPU flag")
This change adds the WQ_UNBOUND flag to explicitly request
alloc_workqueue() to be unbound, because this specific workload has no
benefit being per-cpu.
With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.
Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://lore.kernel.org/r/20251112120125.124578-1-marco.crivellari@suse.com
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The list operation to find and pop transaction entry appears several
times in transaction implementation, and can be replaced with a helper
functional macro.
Link: https://lore.kernel.org/r/20251101102131.925071-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
At present the parameters to compute timeout time for split transaction is
protected by card-wide spin lock, while it is not necessarily convenient
in a point to narrower critical section.
This commit adds and uses another spin lock specific for the purpose.
Link: https://lore.kernel.org/r/20250915234747.915922-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The list of instance for asynchronous transaction to wait for response
subaction is maintained as a member of fw_card structure. The card-wide
spinlock is used at present for any operation over the list, however it
is not necessarily suited for the purpose.
This commit adds and uses the spin lock specific to maintain the list.
Link: https://lore.kernel.org/r/20250915234747.915922-5-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
At present, the operation for read transaction to topology map register is
not protected by any kind of lock primitives. This causes a potential
problem to result in the mixed content of topology map.
This commit adds and uses spin lock specific to topology map.
Link: https://lore.kernel.org/r/20250915234747.915922-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The former commit has a limitation that only up to 4 FCP address
handlers could be processed per request. Although it suffices for most
use cases, it is technically a regression.
This commit lifts the restriction by reallocating the buffer from kernel
heap when more than 4 handlers are registered. The allocation is performed
within RCU read-side critical section, thus it uses GCP_ATOMIC flag. The
buffer size is rounded up to the next power of two to align with kmalloc
allocation units.
Link: https://lore.kernel.org/r/20250803122015.236493-5-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The former commit added reference counting to ensure safe invocations of
address handlers. Unlike the exclusive-region address handlers, all FCP
address handlers should be called on receiving an FCP request.
This commit uses the part of kernel stack to collect address handlers up
to 4 within the section, then invoke them outside of the section.
Reference counting ensures that each handler remains valid and safe to
call.
Lifting the limitation of supporting only 4 handlers is left for next
work.
Link: https://lore.kernel.org/r/20250803122015.236493-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The previous commit added reference counting to ensure safe invocations of
address handlers.
This commit moves the invocation of handlers for exclusive regions outside
of the RCU read-side critical section. The address handler for the
requested region is selected within the critical section, then invoked
outside of it.
Link: https://lore.kernel.org/r/20250803122015.236493-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The lifetime of address handler has been managed by linked list and RCU.
This approach was introduced in commit 35202f7d84 ("firewire: remove
global lock around address handlers, convert to RCU"). The invocations of
address handler are performed within RCU read-side critical sections.
In commit 57e6d9f85f ("firewire: ohci: use workqueue to handle events
of AR request/response contexts"), the invocations are in a workqueue
context. The approach still imposes limitation that sleeping is not
allowed within RCU read-side critical sections. However, since sleeping
is not permitted within RCU read-side critical sections, this approach
still has a limitation.
This commit adds reference counting to decouple handler invocation from
handler discovery. The linked list and RCU is used to discover the
handlers, while the reference counting is used to invoke them safely.
Link: https://lore.kernel.org/r/20250803122015.236493-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
This commit adds a work item to handle events of 1394 OHCI AR
request/response contexts, and queues the item to the specific workqueue.
The call of struct fw_address_handler.address_callback() is done in the
workqueue when receiving any requests from the remove nodes. Additionally,
the call of struct fw_packet.callback() is done in the workqueue too when
receiving acknowledge to the asynchronous packet for the response
subaction of split transaction to the remote nodes.
Link: https://lore.kernel.org/r/20250615133253.433057-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Move this API to the canonical timer_*() namespace.
[ tglx: Redone against pre rc1 ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com
timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree
over and remove the historical wrapper inlines.
Conversion was done with coccinelle plus manual fixups where necessary.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In core function, the instances of fw_device corresponding to firewire device
node in system are maintained by IDR. As of kernel v6.0, IDR has been
superseded by XArray and deprecated.
This commit replaces the usage of IDR with XArray to maintain the device
instances. The instance of XArray is allocated statically, and
initialized with XA_FLAGS_ALLOC so that the index of allocated entry starts
with zero and available as the minor identifier of device node.
Link: https://lore.kernel.org/r/20240812014251.165492-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The core functions uses spinlock in instance of fw_card structure to
protect concurrent access to properties in the instance.
This commit uses guard macro to maintain the spinlock.
Link: https://lore.kernel.org/r/20240805085408.251763-15-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The core function maintains pending asynchronous transactions by list in
the instance of fw_card. The concurrent access to the list is protected
by spinlock in the instance.
This commit uses guard macro to maintain the spinlock.
Link: https://lore.kernel.org/r/20240805085408.251763-14-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The core function maintains address handlers by list. It is protected by
spinlock to insert and remove entry to the list.
This commit uses guard macro to maintain the spinlock.
Link: https://lore.kernel.org/r/20240805085408.251763-8-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The core function maintains address handlers by list. RCU is utilized
for efficient read access to any entries in the list.
This commit uses guard macro to maintain RCU locking and releasing.
Link: https://lore.kernel.org/r/20240805085408.251763-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The core function provide a kernel API to send phy configuration packet.
Current implementation of the feature uses packet object allocated
statically. The concurrent access to the object is protected by static
mutex.
This commit uses guard macro to maintain the mutex.
Link: https://lore.kernel.org/r/20240805085408.251763-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The asynchronous transmission of phy packet is initiated on one of 1394
OHCI controller, however the existing tracepoints events has the lack of
data about it.
This commit adds card_index member into event structure to store the index
of host controller in use, and prints it.
Link: https://lore.kernel.org/r/20240613131440.431766-7-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The asynchronous transmission of phy packet is initiated on one of 1394
OHCI controller, however the existing tracepoints events has the lack of
data about it.
This commit adds card_index member into event structure to store the index
of host controller in use, and prints it.
Link: https://lore.kernel.org/r/20240613131440.431766-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The asynchronous transaction is initiated on one of 1394 OHCI
controller, however the existing tracepoints events has the lack of data
about it.
This commit adds card_index member into event structure to store the index
of host controller in use, and prints it.
Link: https://lore.kernel.org/r/20240613131440.431766-5-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The asynchronous transaction is initiated on one of 1394 OHCI controller,
however the existing tracepoints events has the lack of data about it.
This commit adds card_index member into event structure to store the index
of host controller in use, and prints it.
Link: https://lore.kernel.org/r/20240613131440.431766-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The asynchronous transaction is initiated on one of 1394 OHCI controller,
however the existing tracepoints events has the lack of data about it.
This commit adds card_index member into event structure to store the index
of host controller in use, and prints it.
Link: https://lore.kernel.org/r/20240613131440.431766-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
The asynchronous transaction is initiated on one of 1394 OHCI controller,
however the existing tracepoints events has the lack of data about it.
This commit adds card_index member into event structure to store the index
of host controller in use, and prints it.
Link: https://lore.kernel.org/r/20240613131440.431766-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
This reverts commit 6732491243045f5a7e1995b4be5f3c964b579ebd.
The former commit adds some alternative tracepoints events to replace the
reverted kernel log messages.
Link: https://lore.kernel.org/r/20240501073238.72769-5-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
At the former commit, a pair of tracepoints events is added to trace
asynchronous outbound phy packet. This commit adds a tracepoints event
to trace inbound phy packet. It includes transaction status as well as
the content of phy packet.
This is an example for Remote Reply Packet as a response to Remote Access
Packet sent by lsfirewirephy command in linux-firewire-utils:
async_phy_inbound: \
packet=0xffff955fc02b4e10 generation=1 status=1 timestamp=0x0619 \
first_quadlet=0x001c8208 second_quadlet=0xffe37df7
Link: https://lore.kernel.org/r/20240430001404.734657-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In IEEE 1394 bus, the type of asynchronous packet without any offset to
node address space is called as phy packet. The destination of packet is
IEEE 1394 phy itself. This type of packet is used for several purposes,
mainly for selfID at the state of bus reset, to force selection of root
node, and to adjust gap count.
This commit adds tracepoints events for the type of asynchronous outbound
packet. Like asynchronous outbound transaction packets, a pair of events
are added to trace initiation and completion of transmission.
In the case that the phy packet is sent by kernel API, the match between
the initiation and completion is not so easy, since the data of
'struct fw_packet' is allocated statically. In the case that it is sent by
userspace applications via cdev, the match is easy, since the data is
allocated per each.
This example is for Remote Access Packet by lsfirewirephy command in
linux-firewire-utils:
async_phy_outbound_initiate: \
packet=0xffff89fb34e42e78 generation=1 first_quadlet=0x00148200 \
second_quadlet=0xffeb7dff
async_phy_outbound_complete: \
packet=0xffff89fb34e42e78 generation=1 status=1 timestamp=0x0619
Link: https://lore.kernel.org/r/20240430001404.734657-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In a view of core transaction service, the asynchronous outbound response
consists of two stages; initiation and completion.
This commit adds a pair of events for the asynchronous outbound response.
The following example is for asynchronous write quadlet request as IEC
61883-1 FCP response to node 0xffc1.
async_response_outbound_initiate: \
transaction=0xffff89fa08cf16c0 generation=4 scode=2 dst_id=0xffc1 \
tlabel=25 tcode=2 src_id=0xffc0 rcode=0 \
header={0xffc16420,0xffc00000,0x0,0x0} data={}
async_response_outbound_complete: \
transaction=0xffff89fa08cf16c0 generation=4 scode=2 status=1 \
timestamp=0x0000
Link: https://lore.kernel.org/r/20240429043218.609398-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
This commit adds an event for asynchronous inbound request.
The following example is for asynchronous block write request as IEC
61883-1 FCP request from node 0xffc1.
async_request_inbound: \
transaction=0xffff89fa08cf16c0 generation=4 scode=2 status=2 \
timestamp=0x00b3 dst_id=0xffc0 tlabel=19 tcode=1 src_id=0xffc1 \
offset=0xfffff0000d00 header={0xffc04d10,0xffc1ffff,0xf0000d00,0x80000} \
data={0x19ff08,0xffff0090}
Link: https://lore.kernel.org/r/20240429043218.609398-5-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In the transaction of IEEE 1394, the node to receive the asynchronous
request transfers any response packet to the requester except for the
unified transaction.
This commit adds an event for the inbound packet. Note that the code to
decode the packet header is moved, against the note about the sanity
check.
The following example is for asynchronous lock response with
compare_and_swap code.
async_response_inbound: \
transaction=0xffff955fc6a07a10 generation=5 scode=2 status=1 \
timestamp=0x0089 dst_id=0xffc1 tlabel=54 tcode=11 src_id=0xffc0 \
rcode=0 header={0xffc1d9b0,0xffc00000,0x0,0x40002} data={0x50800080}
Link: https://lore.kernel.org/r/20240429043218.609398-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In a view of core transaction service, the asynchronous outbound request
consists of two stages; initiation and completion. This commit adds a pair
of event for them.
The following example is for asynchronous lock request with compare_swap
code to offset 0x'ffff'f000'0904 in node 0xffc0.
async_request_outbound_initiate: \
transaction=0xffff955fc6a07a10 generation=5 scode=2 dst_id=0xffc0 \
tlabel=54 tcode=9 src_id=0xffc1 offset=0xfffff0000904 \
header={0xffc0d990,0xffc1ffff,0xf0000904,0x80002}
data={0x80,0x940181}
async_request_outbound_complete: \
transaction=0xffff955fc6a07a10 generation=5 scode=2 status=2 \
timestamp=0xd887
Link: https://lore.kernel.org/r/20240429043218.609398-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Add a debug parameter to firewire-core, analogous to the one in
firewire-ohci. When this is set to 1, log when we schedule, delay, or
initiate a bus reset. Since FireWire bus resets can originate from any
node on the bus, specific logging of the resets we initiate provides
additional insight.
Signed-off-by: Adam Goldman <adamg@pobox.com>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In the previous commit, the core function of Linux FireWire subsystem
was changed for two cases to operate asynchronous transaction with or
without time stamp.
This commit changes kernel API for the two cases. Current kernel API,
fw_send_request(), is changed to be static inline function to call
__fw_send_request(), which receives two argument for union and flag of
callback function. The new kernel API, fw_send_request_with_tstamp() is
also added as static inline function, too. When calling, the two
arguments are copied to internal structure, then used in softIRQ
context.
Link: https://lore.kernel.org/r/20230529113406.986289-7-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In 1394 OHCI, the OUTPUT_LAST descriptor of Asynchronous Transmit (AT)
request context has timeStamp field, in which 1394 OHCI controller
record the isochronous cycle when the packet was sent for the request
subaction. Additionally, for the case of split transaction in IEEE 1394,
Asynchronous Receive (AT) request context is used for response subaction
to finish the transaction. The trailer quadlet of descriptor in the
context has timeStamp field, in which 1394 OHCI controller records the
isochronous cycle when the packet arrived.
Current implementation of 1394 OHCI controller driver stores values of
both fields to internal structure as time stamp, while Linux FireWire
subsystem provides no way to access to it. When using asynchronous
transaction service provided by the subsystem, callback function is passed
to kernel API. The prototype of callback function has the lack of argument
for the values.
This commit adds a new callback function for the purpose. It has an
additional argument to point to the constant array with two elements. For
backward compatibility to kernel space, a new union is also adds to wrap
two different prototype of callback function. The fw_transaction structure
has the union as a member and a boolean flag to express which function
callback is available.
The core function is changed to handle the two cases; with or without
time stamp. For the error path to process transaction, the isochronous
cycle is computed by current value of CYCLE_TIMER register in 1394 OHCI
controller. Especially for the case of timeout of split transaction, the
expected isochronous cycle is computed.
Link: https://lore.kernel.org/r/20230529113406.986289-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
In the character device, the listener to address space should distinguish
whether the request is to IEC 61883-1 FCP region or not. The user space
application needs to access to the object of request in enough later by
read(2), while the core function releases the object of request in the FCP
case after completing the callback to handler.
The handler guarantees the access safe by some way. It's done by
duplication of the object after NULL check to the request, since core
function passes NULL in the FCP case. It's inconvenient since the object
of request includes some helpful information. It's better to add another
way to check whether the request is to FCP region or not.
Conveniently the file of transaction layer includes local implementation
for the purpose. This commit moves it to module local file and use it
instead of the NULL check, then the result of check is stored to
per-client data for the inbound transaction so that the result can be
referred by later to release the data.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230120090344.296451-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Developers have acknowledged that maintenance of lifetime for
fw_transaction structure is effective when handling asynchronous
transaction to IEC 61883-1 FCP region, since the core function allows
multiples listeners to the region. Some of them needs to access to the
payload of request in process context after the callback to listener,
while the core function releases the object for the structure just after
completing the callbacks to listeners.
One of the listeners is character device. Current implementation of the
character device duplicates the object for the payload of transaction,
while it's a cost in kernel memory consumption. The lifetime management
can reduce it.
The typical way to maintain the lifetime is reference count. This commit
uses kref structure as a first step for the purpose.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230120090344.296451-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Takashi Sakamoto
Linus Torvalds
Marco Crivellari
Ingo Molnar
Thomas Gleixner
Adam Goldman
Takashi Iwai