This is a note to let you know that I've just added the patch titled
ice: make writes to /dev/gnssX synchronous
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ice-make-writes-to-dev-gnssx-synchronous.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b5737a06c3187f09bc129da0dcc82892975463c9
Author: Michal Schmidt <mschmidt@xxxxxxxxxx>
Date: Tue Jun 6 10:12:53 2023 -0700
ice: make writes to /dev/gnssX synchronous
[ Upstream commit bf15bb38ec7f4ff522da5c20e1673dbda7159938 ]
The current ice driver's GNSS write implementation buffers writes and
works through them asynchronously in a kthread. That's bad because:
- The GNSS write_raw operation is supposed to be synchronous[1][2].
- There is no upper bound on the number of pending writes.
Userspace can submit writes much faster than the driver can process,
consuming unlimited amounts of kernel memory.
A patch that's currently on review[3] ("[v3,net] ice: Write all GNSS
buffers instead of first one") would add one more problem:
- The possibility of waiting for a very long time to flush the write
work when doing rmmod, softlockups.
To fix these issues, simplify the implementation: Drop the buffering,
the write_work, and make the writes synchronous.
I tested this with gpsd and ubxtool.
[1] https://events19.linuxfoundation.org/wp-content/uploads/2017/12/The-GNSS-Subsystem-Johan-Hovold-Hovold-Consulting-AB.pdf
"User interface" slide.
[2] A comment in drivers/gnss/core.c:gnss_write():
/* Ignoring O_NONBLOCK, write_raw() is synchronous. */
[3] https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20230217120541.16745-1-karol.kolacinski@xxxxxxxxx/
Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
Signed-off-by: Michal Schmidt <mschmidt@xxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Tested-by: Sunitha Mekala <sunithax.d.mekala@xxxxxxxxx> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index c2fda4fa4188c..b534d7726d3e8 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -5169,7 +5169,7 @@ ice_aq_read_i2c(struct ice_hw *hw, struct ice_aqc_link_topo_addr topo_addr,
*/
int
ice_aq_write_i2c(struct ice_hw *hw, struct ice_aqc_link_topo_addr topo_addr,
- u16 bus_addr, __le16 addr, u8 params, u8 *data,
+ u16 bus_addr, __le16 addr, u8 params, const u8 *data,
struct ice_sq_cd *cd)
{
struct ice_aq_desc desc = { 0 };
diff --git a/drivers/net/ethernet/intel/ice/ice_common.h b/drivers/net/ethernet/intel/ice/ice_common.h
index 8ba5f935a092b..81961a7d65985 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.h
+++ b/drivers/net/ethernet/intel/ice/ice_common.h
@@ -229,7 +229,7 @@ ice_aq_read_i2c(struct ice_hw *hw, struct ice_aqc_link_topo_addr topo_addr,
struct ice_sq_cd *cd);
int
ice_aq_write_i2c(struct ice_hw *hw, struct ice_aqc_link_topo_addr topo_addr,
- u16 bus_addr, __le16 addr, u8 params, u8 *data,
+ u16 bus_addr, __le16 addr, u8 params, const u8 *data,
struct ice_sq_cd *cd);
bool ice_fw_supports_report_dflt_cfg(struct ice_hw *hw);
#endif /* _ICE_COMMON_H_ */
diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.c b/drivers/net/ethernet/intel/ice/ice_gnss.c
index 8dec748bb53a4..12086aafb42fb 100644
--- a/drivers/net/ethernet/intel/ice/ice_gnss.c
+++ b/drivers/net/ethernet/intel/ice/ice_gnss.c
@@ -16,8 +16,8 @@
* * number of bytes written - success
* * negative - error code
*/
-static unsigned int
-ice_gnss_do_write(struct ice_pf *pf, unsigned char *buf, unsigned int size)
+static int
+ice_gnss_do_write(struct ice_pf *pf, const unsigned char *buf, unsigned int size)
{
struct ice_aqc_link_topo_addr link_topo;
struct ice_hw *hw = &pf->hw;
@@ -72,39 +72,7 @@ ice_gnss_do_write(struct ice_pf *pf, unsigned char *buf, unsigned int size)
dev_err(ice_pf_to_dev(pf), "GNSS failed to write, offset=%u, size=%u, err=%d\n",
offset, size, err);
- return offset;
-}
-
-/**
- * ice_gnss_write_pending - Write all pending data to internal GNSS
- * @work: GNSS write work structure
- */
-static void ice_gnss_write_pending(struct kthread_work *work)
-{
- struct gnss_serial *gnss = container_of(work, struct gnss_serial,
- write_work);
- struct ice_pf *pf = gnss->back;
-
- if (!pf)
- return;
-
- if (!test_bit(ICE_FLAG_GNSS, pf->flags))
- return;
-
- if (!list_empty(&gnss->queue)) {
- struct gnss_write_buf *write_buf = NULL;
- unsigned int bytes;
-
- write_buf = list_first_entry(&gnss->queue,
- struct gnss_write_buf, queue);
-
- bytes = ice_gnss_do_write(pf, write_buf->buf, write_buf->size);
- dev_dbg(ice_pf_to_dev(pf), "%u bytes written to GNSS\n", bytes);
-
- list_del(&write_buf->queue);
- kfree(write_buf->buf);
- kfree(write_buf);
- }
+ return err;
}
/**
@@ -224,8 +192,6 @@ static struct gnss_serial *ice_gnss_struct_init(struct ice_pf *pf)
pf->gnss_serial = gnss;
kthread_init_delayed_work(&gnss->read_work, ice_gnss_read);
- INIT_LIST_HEAD(&gnss->queue);
- kthread_init_work(&gnss->write_work, ice_gnss_write_pending);
kworker = kthread_create_worker(0, "ice-gnss-%s", dev_name(dev));
if (IS_ERR(kworker)) {
kfree(gnss);
@@ -285,7 +251,6 @@ static void ice_gnss_close(struct gnss_device *gdev)
if (!gnss)
return;
- kthread_cancel_work_sync(&gnss->write_work);
kthread_cancel_delayed_work_sync(&gnss->read_work);
}
@@ -304,10 +269,7 @@ ice_gnss_write(struct gnss_device *gdev, const unsigned char *buf,
size_t count)
{
struct ice_pf *pf = gnss_get_drvdata(gdev);
- struct gnss_write_buf *write_buf;
struct gnss_serial *gnss;
- unsigned char *cmd_buf;
- int err = count;
/* We cannot write a single byte using our I2C implementation. */
if (count <= 1 || count > ICE_GNSS_TTY_WRITE_BUF)
@@ -323,24 +285,7 @@ ice_gnss_write(struct gnss_device *gdev, const unsigned char *buf,
if (!gnss)
return -ENODEV;
- cmd_buf = kcalloc(count, sizeof(*buf), GFP_KERNEL);
- if (!cmd_buf)
- return -ENOMEM;
-
- memcpy(cmd_buf, buf, count);
- write_buf = kzalloc(sizeof(*write_buf), GFP_KERNEL);
- if (!write_buf) {
- kfree(cmd_buf);
- return -ENOMEM;
- }
-
- write_buf->buf = cmd_buf;
- write_buf->size = count;
- INIT_LIST_HEAD(&write_buf->queue);
- list_add_tail(&write_buf->queue, &gnss->queue);
- kthread_queue_work(gnss->kworker, &gnss->write_work);
-
- return err;
+ return ice_gnss_do_write(pf, buf, count);
}
static const struct gnss_operations ice_gnss_ops = {
@@ -436,7 +381,6 @@ void ice_gnss_exit(struct ice_pf *pf)
if (pf->gnss_serial) {
struct gnss_serial *gnss = pf->gnss_serial;
- kthread_cancel_work_sync(&gnss->write_work);
kthread_cancel_delayed_work_sync(&gnss->read_work);
kthread_destroy_worker(gnss->kworker);
gnss->kworker = NULL;
diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.h b/drivers/net/ethernet/intel/ice/ice_gnss.h
index 4d49e5b0b4b81..d95ca3928b2ea 100644
--- a/drivers/net/ethernet/intel/ice/ice_gnss.h
+++ b/drivers/net/ethernet/intel/ice/ice_gnss.h
@@ -23,26 +23,16 @@
#define ICE_MAX_UBX_READ_TRIES 255
#define ICE_MAX_UBX_ACK_READ_TRIES 4095
-struct gnss_write_buf {
- struct list_head queue;
- unsigned int size;
- unsigned char *buf;
-};
-
/**
* struct gnss_serial - data used to initialize GNSS TTY port
* @back: back pointer to PF
* @kworker: kwork thread for handling periodic work
* @read_work: read_work function for handling GNSS reads
- * @write_work: write_work function for handling GNSS writes
- * @queue: write buffers queue
*/
struct gnss_serial {
struct ice_pf *back;
struct kthread_worker *kworker;
struct kthread_delayed_work read_work;
- struct kthread_work write_work;
- struct list_head queue;
};
#if IS_ENABLED(CONFIG_GNSS)
