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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-17 12:38:17 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-22 09:16:40 +0200
commit8c071b0f19dfa230335d22ce56a8fab5bd20cedc (patch)
treeffd0d6272cd4e3f33b3069b22cb52457030a7f7a /drivers/s390/cio/cio.c
parent9784bd4f1a6ea736ad9bf241f5a965e0a2913a5e (diff)
downloadop-kernel-dev-8c071b0f19dfa230335d22ce56a8fab5bd20cedc.zip
op-kernel-dev-8c071b0f19dfa230335d22ce56a8fab5bd20cedc.tar.gz
s390/time: correct use of store clock fast
The result of the store-clock-fast (STCKF) instruction is a bit fuzzy. It can happen that the value stored on one CPU is smaller than the value stored on another CPU, although the order of the stores is the other way around. This can cause deltas of get_tod_clock() values to become negative when they should not be. We need to be more careful with store-clock-fast, this patch partially reverts git commit e4b7b4238e666682555461fa52eecd74652f36bb "time: always use stckf instead of stck if available". The get_tod_clock() function now uses the store-clock-extended (STCKE) instruction. get_tod_clock_fast() can be used if the fuzziness of store-clock-fast is acceptable e.g. for wait loops local to a CPU. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'drivers/s390/cio/cio.c')
-rw-r--r--drivers/s390/cio/cio.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c
index d7da67a..88e35d8 100644
--- a/drivers/s390/cio/cio.c
+++ b/drivers/s390/cio/cio.c
@@ -878,9 +878,9 @@ static void css_reset(void)
atomic_inc(&chpid_reset_count);
}
/* Wait for machine check for all channel paths. */
- timeout = get_tod_clock() + (RCHP_TIMEOUT << 12);
+ timeout = get_tod_clock_fast() + (RCHP_TIMEOUT << 12);
while (atomic_read(&chpid_reset_count) != 0) {
- if (get_tod_clock() > timeout)
+ if (get_tod_clock_fast() > timeout)
break;
cpu_relax();
}
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