[Skiboot] [PATCH] Don't detect lock timeouts when timebase is invalid

[Stewart Smith]

We can have threads waiting on hmi_lock who have an
invalid timebase. Because of this, we want to go poke
the register directly rather than rely on
this_cpu()->tb_invalid (which won't have been set yet).

Without this patch, you get something like this when
you're injecting timebase errors:
[10976.202052846,4] WARNING: Lock has been spinning for 10976394ms

Fixes: 84186ef0944c9413262f0974ddab3fb1343ccfe8
Signed-off-by: Stewart Smith <stewart at linux.vnet.ibm.com>
---
 core/lock.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/core/lock.c b/core/lock.c
index 2d94ebb4e285..318f42d92d51 100644
--- a/core/lock.c
+++ b/core/lock.c
@@ -140,6 +140,13 @@ static inline bool lock_timeout(unsigned long start)
 	unsigned long wait = tb_to_msecs(mftb());
 
 	if (wait - start > LOCK_TIMEOUT_MS) {
+		/*
+		 * If the timebase is invalid, we shouldn't
+		 * throw an error. This is possible with pending HMIs
+		 * that need to recover TB.
+		 */
+		if( !(mfspr(SPR_TFMR) & SPR_TFMR_TB_VALID))
+			return false;
 		prlog(PR_WARNING, "WARNING: Lock has been "\
 		      "spinning for %lums\n", wait - start);
 		backtrace();
-- 
2.14.3