4.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Douglas Anderson <diand...@chromium.org> commit 2d13bb6494c807bcf3f78af0e96c0b8615a94385 upstream. We've got a delay loop waiting for secondary CPUs. That loop uses loops_per_jiffy. However, loops_per_jiffy doesn't actually mean how many tight loops make up a jiffy on all architectures. It is quite common to see things like this in the boot log: Calibrating delay loop (skipped), value calculated using timer frequency.. 48.00 BogoMIPS (lpj=24000) In my case I was seeing lots of cases where other CPUs timed out entering the debugger only to print their stack crawls shortly after the kdb> prompt was written. Elsewhere in kgdb we already use udelay(), so that should be safe enough to use to implement our timeout. We'll delay 1 ms for 1000 times, which should give us a full second of delay (just like the old code wanted) but allow us to notice that we're done every 1 ms. [a...@linux-foundation.org: simplifications, per Daniel] Link: http://lkml.kernel.org/r/1477091361-2039-1-git-send-email-diand...@chromium.org Signed-off-by: Douglas Anderson <diand...@chromium.org> Reviewed-by: Daniel Thompson <daniel.thomp...@linaro.org> Cc: Jason Wessel <jason.wes...@windriver.com> Cc: Brian Norris <briannor...@chromium.org> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- kernel/debug/debug_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -598,11 +598,11 @@ return_normal: /* * Wait for the other CPUs to be notified and be waiting for us: */ - time_left = loops_per_jiffy * HZ; + time_left = MSEC_PER_SEC; while (kgdb_do_roundup && --time_left && (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != online_cpus) - cpu_relax(); + udelay(1000); if (!time_left) pr_crit("Timed out waiting for secondary CPUs.\n");
