From mboxrd@z Thu Jan 1 00:00:00 1970 From: guohanjun@huawei.com (Hanjun Guo) Date: Thu, 20 Oct 2016 20:05:35 +0800 Subject: [PATCH 1/2] arm64/numa: fix pcpu_cpu_distance() to get correct CPU proximity In-Reply-To: <20161020104815.GC24914@arm.com> References: <1476935576-59941-1-git-send-email-guohanjun@huawei.com> <20161020104815.GC24914@arm.com> Message-ID: <5808B30F.7040300@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2016/10/20 18:48, Will Deacon wrote: > On Thu, Oct 20, 2016 at 11:52:55AM +0800, Hanjun Guo wrote: >> From: Yisheng Xie >> >> The pcpu_build_alloc_info() function group CPUs according to their >> proximity, by call callback function @cpu_distance_fn from different >> ARCHs. >> >> For arm64 the callback of @cpu_distance_fn is >> pcpu_cpu_distance(from, to) >> -> node_distance(from, to) >> The @from and @to for function node_distance() should be nid. >> >> However, pcpu_cpu_distance() in arch/arm64/mm/numa.c just past the >> cpu id for @from and @to. >> >> For this incorrect cpu proximity get from ARCH, it may cause each CPU >> in one group and make group_cnt out of bound: >> >> setup_per_cpu_areas() >> pcpu_embed_first_chunk() >> pcpu_build_alloc_info() >> in pcpu_build_alloc_info, since cpu_distance_fn will return >> REMOTE_DISTANCE if we pass cpu ids (0,1,2...), so >> cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE will wrongly be ture. >> >> This may results in triggering the BUG_ON(unit != nr_units) later: >> >> [ 0.000000] kernel BUG at mm/percpu.c:1916! >> [ 0.000000] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP >> [ 0.000000] Modules linked in: >> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.9.0-rc1-00003-g14155ca-dirty #26 >> [ 0.000000] Hardware name: Hisilicon Hi1616 Evaluation Board (DT) >> [ 0.000000] task: ffff000008d6e900 task.stack: ffff000008d60000 >> [ 0.000000] PC is at pcpu_embed_first_chunk+0x420/0x704 >> [ 0.000000] LR is at pcpu_embed_first_chunk+0x3bc/0x704 >> [ 0.000000] pc : [] lr : [] pstate: 800000c5 >> [ 0.000000] sp : ffff000008d63eb0 >> [ 0.000000] x29: ffff000008d63eb0 [ 0.000000] x28: 0000000000000000 >> [ 0.000000] x27: 0000000000000040 [ 0.000000] x26: ffff8413fbfcef00 >> [ 0.000000] x25: 0000000000000042 [ 0.000000] x24: 0000000000000042 >> [ 0.000000] x23: 0000000000001000 [ 0.000000] x22: 0000000000000046 >> [ 0.000000] x21: 0000000000000001 [ 0.000000] x20: ffff000008cb3bc8 >> [ 0.000000] x19: ffff8413fbfcf570 [ 0.000000] x18: 0000000000000000 >> [ 0.000000] x17: ffff000008e49ae0 [ 0.000000] x16: 0000000000000003 >> [ 0.000000] x15: 000000000000001e [ 0.000000] x14: 0000000000000004 >> [ 0.000000] x13: 0000000000000000 [ 0.000000] x12: 000000000000006f >> [ 0.000000] x11: 00000413fbffff00 [ 0.000000] x10: 0000000000000004 >> [ 0.000000] x9 : 0000000000000000 [ 0.000000] x8 : 0000000000000001 >> [ 0.000000] x7 : ffff8413fbfcf63c [ 0.000000] x6 : ffff000008d65d28 >> [ 0.000000] x5 : ffff000008d65e50 [ 0.000000] x4 : 0000000000000000 >> [ 0.000000] x3 : ffff000008cb3cc8 [ 0.000000] x2 : 0000000000000040 >> [ 0.000000] x1 : 0000000000000040 [ 0.000000] x0 : 0000000000000000 >> [...] >> [ 0.000000] Call trace: >> [ 0.000000] Exception stack(0xffff000008d63ce0 to 0xffff000008d63e10) >> [ 0.000000] 3ce0: ffff8413fbfcf570 0001000000000000 ffff000008d63eb0 ffff000008c754f4 >> [ 0.000000] 3d00: ffff000008d63d50 ffff0000081af210 00000413fbfff010 0000000000001000 >> [ 0.000000] 3d20: ffff000008d63d50 ffff0000081af220 00000413fbfff010 0000000000001000 >> [ 0.000000] 3d40: 00000413fbfcef00 0000000000000004 ffff000008d63db0 ffff0000081af390 >> [ 0.000000] 3d60: 00000413fbfcef00 0000000000001000 0000000000000000 0000000000001000 >> [ 0.000000] 3d80: 0000000000000000 0000000000000040 0000000000000040 ffff000008cb3cc8 >> [ 0.000000] 3da0: 0000000000000000 ffff000008d65e50 ffff000008d65d28 ffff8413fbfcf63c >> [ 0.000000] 3dc0: 0000000000000001 0000000000000000 0000000000000004 00000413fbffff00 >> [ 0.000000] 3de0: 000000000000006f 0000000000000000 0000000000000004 000000000000001e >> [ 0.000000] 3e00: 0000000000000003 ffff000008e49ae0 >> [ 0.000000] [] pcpu_embed_first_chunk+0x420/0x704 >> [ 0.000000] [] setup_per_cpu_areas+0x38/0xc8 >> [ 0.000000] [] start_kernel+0x10c/0x390 >> [ 0.000000] [] __primary_switched+0x5c/0x64 >> [ 0.000000] Code: b8018660 17ffffd7 6b16037f 54000080 (d4210000) >> [ 0.000000] ---[ end trace 0000000000000000 ]--- >> [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! >> >> Fix by getting CPUs proximity through its node. We only care about >> whether it is LOCAL_DISTANCE or not, for pcpu_build_alloc_info() only >> use this to group CPUs. >> >> Fixes: 7af3a0a99252 ("arm64/numa: support HAVE_SETUP_PER_CPU_AREA") >> Signed-off-by: Yisheng Xie >> Signed-off-by: Hanjun Guo >> Cc: Catalin Marinas >> Cc: Lorenzo Pieralisi >> Cc: Will Deacon >> Cc: Zhen Lei >> --- >> arch/arm64/mm/numa.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c >> index 778a985..34415fc 100644 >> --- a/arch/arm64/mm/numa.c >> +++ b/arch/arm64/mm/numa.c >> @@ -147,7 +147,10 @@ static int __init early_cpu_to_node(int cpu) >> >> static int __init pcpu_cpu_distance(unsigned int from, unsigned int to) >> { >> - return node_distance(from, to); >> + if (early_cpu_to_node(from) == early_cpu_to_node(to)) >> + return LOCAL_DISTANCE; >> + else >> + return REMOTE_DISTANCE; > Why can't this be node_distance(early_cpu_to_node(from), early_cpu_to_node(to))? It's really some coding style preference and the caller function is only care about it's LOCAL_DISTANCE or not, as we said in the commit message. But using node_distance() will save few lines of code and no functional change, will update it. Thanks Hanjun