diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2025-08-11 10:27:45 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-13 17:18:43 +0200 |
| commit | 9528d32873b38281ae105f2f5799e79ae9d086c2 (patch) | |
| tree | e811edf0b4f591c28e383acbb195f7534b2eeb49 /drivers/usb/core | |
| parent | 86f390ba59cd8d5755bafe2b163c3e6b89d6bbd9 (diff) | |
kcov, usb: Don't disable interrupts in kcov_remote_start_usb_softirq()
kcov_remote_start_usb_softirq() the begin of urb's completion callback.
HCDs marked HCD_BH will invoke this function from the softirq and
in_serving_softirq() will detect this properly.
Root-HUB (RH) requests will not be delayed to softirq but complete
immediately in IRQ context.
This will confuse kcov because in_serving_softirq() will report true if
the softirq is served after the hardirq and if the softirq got
interrupted by the hardirq in which currently runs.
This was addressed by simply disabling interrupts in
kcov_remote_start_usb_softirq() which avoided the interruption by the RH
while a regular completion callback was invoked.
This not only changes the behaviour while kconv is enabled but also
breaks PREEMPT_RT because now sleeping locks can no longer be acquired.
Revert the previous fix. Address the issue by invoking
kcov_remote_start_usb() only if the context is just "serving softirqs"
which is identified by checking in_serving_softirq() and in_hardirq()
must be false.
Fixes: f85d39dd7ed89 ("kcov, usb: disable interrupts in kcov_remote_start_usb_softirq")
Cc: stable <stable@kernel.org>
Reported-by: Yunseong Kim <ysk@kzalloc.com>
Closes: https://lore.kernel.org/all/20250725201400.1078395-2-ysk@kzalloc.com/
Tested-by: Yunseong Kim <ysk@kzalloc.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250811082745.ycJqBXMs@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/core')
| -rw-r--r-- | drivers/usb/core/hcd.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index c4a1875b5d3d..6270fbb5c699 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1636,7 +1636,6 @@ static void __usb_hcd_giveback_urb(struct urb *urb) struct usb_hcd *hcd = bus_to_hcd(urb->dev->bus); struct usb_anchor *anchor = urb->anchor; int status = urb->unlinked; - unsigned long flags; urb->hcpriv = NULL; if (unlikely((urb->transfer_flags & URB_SHORT_NOT_OK) && @@ -1654,14 +1653,13 @@ static void __usb_hcd_giveback_urb(struct urb *urb) /* pass ownership to the completion handler */ urb->status = status; /* - * Only collect coverage in the softirq context and disable interrupts - * to avoid scenarios with nested remote coverage collection sections - * that KCOV does not support. - * See the comment next to kcov_remote_start_usb_softirq() for details. + * This function can be called in task context inside another remote + * coverage collection section, but kcov doesn't support that kind of + * recursion yet. Only collect coverage in softirq context for now. */ - flags = kcov_remote_start_usb_softirq((u64)urb->dev->bus->busnum); + kcov_remote_start_usb_softirq((u64)urb->dev->bus->busnum); urb->complete(urb); - kcov_remote_stop_softirq(flags); + kcov_remote_stop_softirq(); usb_anchor_resume_wakeups(anchor); atomic_dec(&urb->use_count); |