From: Fabian Grünbichler Date: Thu, 14 Jul 2016 14:00:19 +0000 (+0200) Subject: add scheduler fix for ceph on numa hosts X-Git-Url: https://git.proxmox.com/?p=pve-kernel-jessie.git;a=commitdiff_plain;h=e55267fc08bce97a83bb345eac189c86ecaff35c add scheduler fix for ceph on numa hosts see https://forum.proxmox.com/threads/ceph-kernel-4-4-8-bug.28196/ and https://lkml.org/lkml/2016/3/17/570 for background --- diff --git a/Makefile b/Makefile index 6b3cd6b..b4320bc 100644 --- a/Makefile +++ b/Makefile @@ -258,6 +258,7 @@ ${KERNEL_SRC}/README ${KERNEL_CFG_ORG}: ${KERNELSRCTAR} cd ${KERNEL_SRC}; patch -p1 < ../CVE-2016-4794-1-percpu-fix-synchronization-between-chunk-map_extend_.patch cd ${KERNEL_SRC}; patch -p1 < ../CVE-2016-4794-2-percpu-fix-synchronization-between-synchronous-map-e.patch cd ${KERNEL_SRC}; patch -p1 < ../CVE-2016-4470-KEYS-potential-uninitialized-variable.patch + cd ${KERNEL_SRC}; patch -p1 < ../ceph-scheduler-fix.patch sed -i ${KERNEL_SRC}/Makefile -e 's/^EXTRAVERSION.*$$/EXTRAVERSION=${EXTRAVERSION}/' touch $@ diff --git a/ceph-scheduler-fix.patch b/ceph-scheduler-fix.patch new file mode 100644 index 0000000..2466f82 --- /dev/null +++ b/ceph-scheduler-fix.patch @@ -0,0 +1,137 @@ +commit 8974189222159154c55f24ddad33e3613960521a +Author: Peter Zijlstra +Date: Thu Jun 16 10:50:40 2016 +0200 + + sched/fair: Fix cfs_rq avg tracking underflow + + As per commit: + + b7fa30c9cc48 ("sched/fair: Fix post_init_entity_util_avg() serialization") + + > the code generated from update_cfs_rq_load_avg(): + > + > if (atomic_long_read(&cfs_rq->removed_load_avg)) { + > s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0); + > sa->load_avg = max_t(long, sa->load_avg - r, 0); + > sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0); + > removed_load = 1; + > } + > + > turns into: + > + > ffffffff81087064: 49 8b 85 98 00 00 00 mov 0x98(%r13),%rax + > ffffffff8108706b: 48 85 c0 test %rax,%rax + > ffffffff8108706e: 74 40 je ffffffff810870b0 + > ffffffff81087070: 4c 89 f8 mov %r15,%rax + > ffffffff81087073: 49 87 85 98 00 00 00 xchg %rax,0x98(%r13) + > ffffffff8108707a: 49 29 45 70 sub %rax,0x70(%r13) + > ffffffff8108707e: 4c 89 f9 mov %r15,%rcx + > ffffffff81087081: bb 01 00 00 00 mov $0x1,%ebx + > ffffffff81087086: 49 83 7d 70 00 cmpq $0x0,0x70(%r13) + > ffffffff8108708b: 49 0f 49 4d 70 cmovns 0x70(%r13),%rcx + > + > Which you'll note ends up with sa->load_avg -= r in memory at + > ffffffff8108707a. + + So I _should_ have looked at other unserialized users of ->load_avg, + but alas. Luckily nikbor reported a similar /0 from task_h_load() which + instantly triggered recollection of this here problem. + + Aside from the intermediate value hitting memory and causing problems, + there's another problem: the underflow detection relies on the signed + bit. This reduces the effective width of the variables, IOW its + effectively the same as having these variables be of signed type. + + This patch changes to a different means of unsigned underflow + detection to not rely on the signed bit. This allows the variables to + use the 'full' unsigned range. And it does so with explicit LOAD - + STORE to ensure any intermediate value will never be visible in + memory, allowing these unserialized loads. + + Note: GCC generates crap code for this, might warrant a look later. + + Note2: I say 'full' above, if we end up at U*_MAX we'll still explode; + maybe we should do clamping on add too. + + Signed-off-by: Peter Zijlstra (Intel) + Cc: Andrey Ryabinin + Cc: Chris Wilson + Cc: Linus Torvalds + Cc: Mike Galbraith + Cc: Peter Zijlstra + Cc: Thomas Gleixner + Cc: Yuyang Du + Cc: bsegall@google.com + Cc: kernel@kyup.com + Cc: morten.rasmussen@arm.com + Cc: pjt@google.com + Cc: steve.muckle@linaro.org + Fixes: 9d89c257dfb9 ("sched/fair: Rewrite runnable load and utilization average tracking") + Link: http://lkml.kernel.org/r/20160617091948.GJ30927@twins.programming.kicks-ass.net + Signed-off-by: Ingo Molnar + +--- + kernel/sched/fair.c | 33 +++++++++++++++++++++++++-------- + 1 file changed, 25 insertions(+), 8 deletions(-) + +--- a/kernel/sched/fair.c ++++ b/kernel/sched/fair.c +@@ -2682,6 +2682,23 @@ static inline void update_tg_load_avg(st + + static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); + ++/* ++ * Unsigned subtract and clamp on underflow. ++ * ++ * Explicitly do a load-store to ensure the intermediate value never hits ++ * memory. This allows lockless observations without ever seeing the negative ++ * values. ++ */ ++#define sub_positive(_ptr, _val) do { \ ++ typeof(_ptr) ptr = (_ptr); \ ++ typeof(*ptr) val = (_val); \ ++ typeof(*ptr) res, var = READ_ONCE(*ptr); \ ++ res = var - val; \ ++ if (res > var) \ ++ res = 0; \ ++ WRITE_ONCE(*ptr, res); \ ++} while (0) ++ + /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */ + static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) + { +@@ -2690,15 +2707,15 @@ static inline int update_cfs_rq_load_avg + + if (atomic_long_read(&cfs_rq->removed_load_avg)) { + s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0); +- sa->load_avg = max_t(long, sa->load_avg - r, 0); +- sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0); ++ sub_positive(&sa->load_avg, r); ++ sub_positive(&sa->load_sum, r * LOAD_AVG_MAX); + removed = 1; + } + + if (atomic_long_read(&cfs_rq->removed_util_avg)) { + long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0); +- sa->util_avg = max_t(long, sa->util_avg - r, 0); +- sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0); ++ sub_positive(&sa->util_avg, r); ++ sub_positive(&sa->util_sum, r * LOAD_AVG_MAX); + } + + decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa, +@@ -2764,10 +2781,10 @@ static void detach_entity_load_avg(struc + &se->avg, se->on_rq * scale_load_down(se->load.weight), + cfs_rq->curr == se, NULL); + +- cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0); +- cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0); +- cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0); +- cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0); ++ sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg); ++ sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum); ++ sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg); ++ sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum); + } + + /* Add the load generated by se into cfs_rq's load average */