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authorDouglas Anderson <dianders@chromium.org>2016-12-14 15:05:49 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-06 10:40:17 +0100
commitf726f4f411f9094a3901fb35985f070c0fdec5b2 (patch)
tree6b52cf3c3e9e3ea6a54c6961a6f57a5d1ce6af7e /kernel
parent9b78d69054243a0d047ebccdd64cb8a2462e174e (diff)
kernel/debug/debug_core.c: more properly delay for secondary CPUs
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. [akpm@linux-foundation.org: simplifications, per Daniel] Link: http://lkml.kernel.org/r/1477091361-2039-1-git-send-email-dianders@chromium.org Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Brian Norris <briannorris@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/debug/debug_core.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 0874e2edd275..79517e5549f1 100644
--- 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");