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authorPeter Zijlstra <peterz@infradead.org>2018-04-05 10:05:21 +0200
committerIngo Molnar <mingo@kernel.org>2018-04-05 10:56:16 +0200
commit317d359df95dd0cb7653d09b7fc513770590cf85 (patch)
tree999cc75a56d86410682a1cb42e372006741ea1d5 /include/linux/sched.h
parentadcc8da8859bee9548bb6d323b1e8de8a7252acd (diff)
sched/core: Force proper alignment of 'struct util_est'
For some as yet not understood reason, Tony gets unaligned access traps on IA64 because of: struct util_est ue = READ_ONCE(p->se.avg.util_est); and: WRITE_ONCE(p->se.avg.util_est, ue); introduced by commit: d519329f72a6 ("sched/fair: Update util_est only on util_avg updates") Normally those two fields should end up on an 8-byte aligned location, but UP and RANDSTRUCT can mess that up so enforce the alignment explicitly. Also make the alignment on sched_avg unconditional, as it is really about data locality, not false-sharing. With or without this patch the layout for sched_avg on a ia64-defconfig build looks like: $ pahole -EC sched_avg ia64-defconfig/kernel/sched/core.o die__process_function: tag not supported (INVALID)! struct sched_avg { /* typedef u64 */ long long unsigned int last_update_time; /* 0 8 */ /* typedef u64 */ long long unsigned int load_sum; /* 8 8 */ /* typedef u64 */ long long unsigned int runnable_load_sum; /* 16 8 */ /* typedef u32 */ unsigned int util_sum; /* 24 4 */ /* typedef u32 */ unsigned int period_contrib; /* 28 4 */ long unsigned int load_avg; /* 32 8 */ long unsigned int runnable_load_avg; /* 40 8 */ long unsigned int util_avg; /* 48 8 */ struct util_est { unsigned int enqueued; /* 56 4 */ unsigned int ewma; /* 60 4 */ } util_est; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ /* size: 64, cachelines: 1, members: 9 */ }; Reported-and-Tested-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Norbert Manthey <nmanthey@amazon.de> Cc: Patrick Bellasi <patrick.bellasi@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony <tony.luck@intel.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Fixes: d519329f72a6 ("sched/fair: Update util_est only on util_avg updates") Link: http://lkml.kernel.org/r/20180405080521.GG4129@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r--include/linux/sched.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f228c6033832..b3d697f3b573 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -300,7 +300,7 @@ struct util_est {
unsigned int enqueued;
unsigned int ewma;
#define UTIL_EST_WEIGHT_SHIFT 2
-};
+} __attribute__((__aligned__(sizeof(u64))));
/*
* The load_avg/util_avg accumulates an infinite geometric series
@@ -364,7 +364,7 @@ struct sched_avg {
unsigned long runnable_load_avg;
unsigned long util_avg;
struct util_est util_est;
-};
+} ____cacheline_aligned;
struct sched_statistics {
#ifdef CONFIG_SCHEDSTATS
@@ -435,7 +435,7 @@ struct sched_entity {
* Put into separate cache line so it does not
* collide with read-mostly values above.
*/
- struct sched_avg avg ____cacheline_aligned_in_smp;
+ struct sched_avg avg;
#endif
};