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. Signed-off-by: Douglas Anderson <diand...@chromium.org> --- Changes in v2: - Use udelay, not __delay kernel/debug/debug_core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 0874e2edd275..85a246feb442 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -61,6 +61,8 @@ #include "debug_core.h" +#define WAIT_CPUS_STOP_MS 1000 + static int kgdb_break_asap; struct debuggerinfo_struct kgdb_info[NR_CPUS]; @@ -598,11 +600,11 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, /* * Wait for the other CPUs to be notified and be waiting for us: */ - time_left = loops_per_jiffy * HZ; + time_left = WAIT_CPUS_STOP_MS; 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"); -- 2.8.0.rc3.226.g39d4020