On Wed, Feb 27, 2019 at 03:19:17PM -0700, Daniel Kurtz wrote: > In cases such as xhci_abort_cmd_ring(), xhci_handshake() is called with > a spin lock held (and local interrupts disabled) with a huge 5 second > timeout. This can translates to 5 million calls to udelay(1). By its > very nature, udelay() is not meant to be precise, it only guarantees to > delay a minimum of 1 microsecond. Therefore the actual delay of > xhci_handshake() can be significantly longer. If the average udelay(1) > is greater than 2.2 us, the total time in xhci_handshake() - with > interrupts disabled can be > 11 seconds triggering the kernel's soft lockup > detector. > > To avoid this, let's replace the open coded io polling loop with one from > iopoll.h that uses a loop timed with the more presumably reliable ktime > infrastructure. > > Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> Looks sane to me, nice fixup. Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Is this causing problems on older kernels/devices today such that we should backport this? thanks, greg k-h
