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spi: Ensure the io_mutex is held until spi_finalize_current_message() 

This patch introduces a completion that is completed in
spi_finalize_current_message() and waited for in
__spi_pump_transfer_message(). This way all manipulation of ctlr->cur_msg
is done with the io_mutex held and strictly ordered:
__spi_pump_transfer_message() will not return until
spi_finalize_current_message() is done using ctlr->cur_msg, and its
calling context is only touching ctlr->cur_msg after returning.
Due to this, we can safely drop the spin-locks around ctlr->cur_msg.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-11-david@protonic.nl
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
David Jander 2022-06-21 08:12:33 +02:00 committed by Mark Brown
parent 72c5c59b65
commit 69fa95905d
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
2 changed files with 16 additions and 22 deletions
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32
drivers/spi/spi.c
View File

@ -1613,11 +1613,14 @@ static int __spi_pump_transfer_message(struct spi_controller *ctlr,
}
}
reinit_completion(&ctlr->cur_msg_completion);
ret = ctlr->transfer_one_message(ctlr, msg);
if (ret) {
dev_err(&ctlr->dev,
"failed to transfer one message from queue\n");
return ret;
} else {
wait_for_completion(&ctlr->cur_msg_completion);
}
return 0;
@ -1704,6 +1707,12 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
spin_unlock_irqrestore(&ctlr->queue_lock, flags);
ret = __spi_pump_transfer_message(ctlr, msg, was_busy);
if (!ret)
kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
ctlr->cur_msg = NULL;
ctlr->fallback = false;
mutex_unlock(&ctlr->io_mutex);
/* Prod the scheduler in case transfer_one() was busy waiting */
@ -1897,12 +1906,9 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
{
struct spi_transfer *xfer;
struct spi_message *mesg;
unsigned long flags;
int ret;
spin_lock_irqsave(&ctlr->queue_lock, flags);
mesg = ctlr->cur_msg;
spin_unlock_irqrestore(&ctlr->queue_lock, flags);
if (!ctlr->ptp_sts_supported && !ctlr->transfer_one) {
list_for_each_entry(xfer, &mesg->transfers, transfer_list) {
@ -1936,20 +1942,7 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
mesg->prepared = false;
if (!mesg->sync) {
/*
* This message was sent via the async message queue. Handle
* the queue and kick the worker thread to do the
* idling/shutdown or send the next message if needed.
*/
spin_lock_irqsave(&ctlr->queue_lock, flags);
WARN(ctlr->cur_msg != mesg,
"Finalizing queued message that is not the current head of queue!");
ctlr->cur_msg = NULL;
ctlr->fallback = false;
kthread_queue_work(ctlr->kworker, &ctlr->pump_messages);
spin_unlock_irqrestore(&ctlr->queue_lock, flags);
}
complete(&ctlr->cur_msg_completion);
trace_spi_message_done(mesg);
@ -3036,6 +3029,7 @@ int spi_register_controller(struct spi_controller *ctlr)
}
ctlr->bus_lock_flag = 0;
init_completion(&ctlr->xfer_completion);
init_completion(&ctlr->cur_msg_completion);
if (!ctlr->max_dma_len)
ctlr->max_dma_len = INT_MAX;
@ -3962,6 +3956,9 @@ static void __spi_transfer_message_noqueue(struct spi_controller *ctlr, struct s
if (ret)
goto out;
ctlr->cur_msg = NULL;
ctlr->fallback = false;
if (!was_busy) {
kfree(ctlr->dummy_rx);
ctlr->dummy_rx = NULL;
@ -4013,7 +4010,6 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
* will catch those cases.
*/
if (READ_ONCE(ctlr->queue_empty)) {
message->sync = true;
message->actual_length = 0;
message->status = -EINPROGRESS;

6
include/linux/spi/spi.h
View File

@ -384,6 +384,7 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
* @queue_lock: spinlock to syncronise access to message queue
* @queue: message queue
* @cur_msg: the currently in-flight message
* @cur_msg_completion: a completion for the current in-flight message
* @cur_msg_mapped: message has been mapped for DMA
* @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
* selected
@ -615,6 +616,7 @@ struct spi_controller {
spinlock_t queue_lock;
struct list_head queue;
struct spi_message *cur_msg;
struct completion cur_msg_completion;
bool busy;
bool running;
bool rt;
@ -989,7 +991,6 @@ struct spi_transfer {
* @state: for use by whichever driver currently owns the message
* @resources: for resource management when the spi message is processed
* @prepared: spi_prepare_message was called for the this message
* @sync: this message took the direct sync path skipping the async queue
*
* A @spi_message is used to execute an atomic sequence of data transfers,
* each represented by a struct spi_transfer. The sequence is "atomic"
@ -1042,9 +1043,6 @@ struct spi_message {
/* spi_prepare_message was called for this message */
bool prepared;
/* this message is skipping the async queue */
bool sync;
};
static inline void spi_message_init_no_memset(struct spi_message *m)