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authorDavid Herrmann <dh.herrmann@gmail.com>2014-07-29 17:14:15 +0200
committerJiri Kosina <jkosina@suse.cz>2014-08-25 03:28:05 -0500
commit0e0d7520064c9f5668c030afafdbcab242176195 (patch)
tree065b9a6d5e0cd495b315040941cc93df32a7617f /drivers/hid/uhid.c
parentcee5aa1f81b1e88d8de05df226bfd207041954c2 (diff)
HID: uhid: simplify report-cb shutdown
The report-query is blocking, so when user-space destroys a device we have to wake up any blocking kernel context that is currently in the report-cb. We used some broken correlation between @report_done and @running so far. Replace it by a much more obvious use. We now wake up the report-cb if either @report_done or @running is set. wake_up() and wait_event() serve as implicit barriers (as they always do) so no need to use smp_rmb/wmb directly. Note that @report_done is never reset by anyone but the report-cb, thus it cannot flip twice while we wait for it. And whenever we set @running, we afterwards synchronously remove the HID device. Therefore, we wait for all report-cbs to finish before we return. This way, @running can never flip to true while we wait for it. Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid/uhid.c')
-rw-r--r--drivers/hid/uhid.c11
1 files changed, 2 insertions, 9 deletions
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 0cb92e347258..16af4d382391 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -172,13 +172,9 @@ static int uhid_hid_get_raw(struct hid_device *hid, unsigned char rnum,
spin_unlock_irqrestore(&uhid->qlock, flags);
ret = wait_event_interruptible_timeout(uhid->report_wait,
- atomic_read(&uhid->report_done), 5 * HZ);
+ atomic_read(&uhid->report_done) || !uhid->running,
+ 5 * HZ);
- /*
- * Make sure "uhid->running" is cleared on shutdown before
- * "uhid->report_done" is set.
- */
- smp_rmb();
if (!ret || !uhid->running) {
ret = -EIO;
} else if (ret < 0) {
@@ -493,10 +489,7 @@ static int uhid_dev_destroy(struct uhid_device *uhid)
if (!uhid->running)
return -EINVAL;
- /* clear "running" before setting "report_done" */
uhid->running = false;
- smp_wmb();
- atomic_set(&uhid->report_done, 1);
wake_up_interruptible(&uhid->report_wait);
hid_destroy_device(uhid->hid);

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