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author | rogersb11 <brettrogers11@gmail.com> | 2015-11-10 11:19:31 -0600 |
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committer | rogersb11 <brettrogers11@gmail.com> | 2015-11-10 14:01:25 -0500 |
commit | b4d16f70c34ecb908c8a61e58ea51fecdd4a4b10 (patch) | |
tree | 973e9aeb97bb13497d17a43e6f3c070381bc5b87 /kernel/sched_clock.c | |
parent | d177fbc2f0c263b06c18bda2eb46200a31bcbebd (diff) | |
parent | 5dba9ddd98cbc7ad319d687887981a0ea0062c75 (diff) | |
download | kernel_samsung_smdk4412-b4d16f70c34ecb908c8a61e58ea51fecdd4a4b10.zip kernel_samsung_smdk4412-b4d16f70c34ecb908c8a61e58ea51fecdd4a4b10.tar.gz kernel_samsung_smdk4412-b4d16f70c34ecb908c8a61e58ea51fecdd4a4b10.tar.bz2 |
Merge remote-tracking branch 'korg/linux-3.0.y' into cm-13.0
Conflicts:
crypto/algapi.c
drivers/gpu/drm/i915/i915_debugfs.c
drivers/gpu/drm/i915/intel_display.c
drivers/video/fbmem.c
include/linux/nls.h
kernel/cgroup.c
kernel/signal.c
kernel/timeconst.pl
net/ipv4/ping.c
Change-Id: I1f532925d1743df74d66bcdd6fc92f05c72ee0dd
Diffstat (limited to 'kernel/sched_clock.c')
-rw-r--r-- | kernel/sched_clock.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index a4cc338..e17ec39 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -164,10 +164,36 @@ static u64 sched_clock_remote(struct sched_clock_data *scd) u64 this_clock, remote_clock; u64 *ptr, old_val, val; +#if BITS_PER_LONG != 64 +again: + /* + * Careful here: The local and the remote clock values need to + * be read out atomic as we need to compare the values and + * then update either the local or the remote side. So the + * cmpxchg64 below only protects one readout. + * + * We must reread via sched_clock_local() in the retry case on + * 32bit as an NMI could use sched_clock_local() via the + * tracer and hit between the readout of + * the low32bit and the high 32bit portion. + */ + this_clock = sched_clock_local(my_scd); + /* + * We must enforce atomic readout on 32bit, otherwise the + * update on the remote cpu can hit inbetween the readout of + * the low32bit and the high 32bit portion. + */ + remote_clock = cmpxchg64(&scd->clock, 0, 0); +#else + /* + * On 64bit the read of [my]scd->clock is atomic versus the + * update, so we can avoid the above 32bit dance. + */ sched_clock_local(my_scd); again: this_clock = my_scd->clock; remote_clock = scd->clock; +#endif /* * Use the opportunity that we have both locks |