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authorMichael Ellerman <mpe@ellerman.id.au>2013-12-23 12:46:05 (GMT)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2014-02-11 00:24:51 (GMT)
commit1507589787529b0d8e2a9e66e0c6f113ecab5181 (patch)
tree69c63b49738951c8403809d3b0edf7b84e745792 /arch/powerpc
parent730efb6193f8568354fd80849612291afa9fa81e (diff)
powerpc/xmon: Fix timeout loop in get_output_lock()
As far as I can tell, our 70s era timeout loop in get_output_lock() is generating no code. This leads to the hostile takeover happening more or less simultaneously on all cpus. The result is "interesting", some example output that is more readable than most: cpu 0x1: Vector: 100 (Scypsut e0mx bR:e setV)e catto xc0p:u[ c 00 c0:0 000t0o0V0erc0td:o5 rfc28050000]0c00 0 0 0 6t(pSrycsV1ppuot uxe 1m 2 0Rx21e3:0s0ce000c00000t00)00 60602oV2SerucSayt0y 0p 1sxs Fix it by using udelay() in the timeout loop. The wait time and check frequency are arbitrary, but seem to work OK. We already rely on udelay() working so this is not a new dependency. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/xmon/xmon.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 598cdc7..d712b23 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -315,10 +315,17 @@ static void get_output_lock(void)
if (last_speaker == 0)
return;
- timeout = 10000000;
+ /*
+ * Wait a full second for the lock, we might be on a slow
+ * console, but check every 100us.
+ */
+ timeout = 10000;
while (xmon_speaker == last_speaker) {
- if (--timeout > 0)
+ if (--timeout > 0) {
+ udelay(100);
continue;
+ }
+
/* hostile takeover */
prev = cmpxchg(&xmon_speaker, last_speaker, me);
if (prev == last_speaker)

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