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dianderstorvalds
dianders
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kernel/debug/debug_core.c: more properly delay for secondary CPUs
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> Cc: <stable@vger.kernel.org> [4.0+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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‎kernel/debug/debug_core.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -598,11 +598,11 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
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/*
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* Wait for the other CPUs to be notified and be waiting for us:
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*/
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time_left = loops_per_jiffy * HZ;
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time_left = MSEC_PER_SEC;
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while (kgdb_do_roundup && --time_left &&
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(atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
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online_cpus)
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cpu_relax();
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udelay(1000);
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if (!time_left)
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pr_crit("Timed out waiting for secondary CPUs.\n");
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