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From d5d5d0c3125cbb6edd6fdf712108af74827b7f59 Mon Sep 17 00:00:00 2001 |
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From: Sasha Levin <sashal@kernel.org> |
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Date: Sat, 12 Feb 2022 22:21:11 +0000 |
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Subject: MIPS: smp: fill in sibling and core maps earlier |
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MIME-Version: 1.0 |
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Content-Type: text/plain; charset=UTF-8 |
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Content-Transfer-Encoding: 8bit |
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|
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From: Alexander Lobakin <alobakin@pm.me> |
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|
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[ Upstream commit f2703def339c793674010cc9f01bfe4980231808 ] |
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|
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After enabling CONFIG_SCHED_CORE (landed during 5.14 cycle), |
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2-core 2-thread-per-core interAptiv (CPS-driven) started emitting |
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the following: |
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|
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[ 0.025698] CPU1 revision is: 0001a120 (MIPS interAptiv (multi)) |
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[ 0.048183] ------------[ cut here ]------------ |
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[ 0.048187] WARNING: CPU: 1 PID: 0 at kernel/sched/core.c:6025 sched_core_cpu_starting+0x198/0x240 |
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[ 0.048220] Modules linked in: |
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[ 0.048233] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc3+ #35 b7b319f24073fd9a3c2aa7ad15fb7993eec0b26f |
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[ 0.048247] Stack : 817f0000 00000004 327804c8 810eb050 00000000 00000004 00000000 c314fdd1 |
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[ 0.048278] 830cbd64 819c0000 81800000 817f0000 83070bf4 00000001 830cbd08 00000000 |
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[ 0.048307] 00000000 00000000 815fcbc4 00000000 00000000 00000000 00000000 00000000 |
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[ 0.048334] 00000000 00000000 00000000 00000000 817f0000 00000000 00000000 817f6f34 |
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[ 0.048361] 817f0000 818a3c00 817f0000 00000004 00000000 00000000 4dc33260 0018c933 |
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[ 0.048389] ... |
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[ 0.048396] Call Trace: |
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[ 0.048399] [<8105a7bc>] show_stack+0x3c/0x140 |
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[ 0.048424] [<8131c2a0>] dump_stack_lvl+0x60/0x80 |
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[ 0.048440] [<8108b5c0>] __warn+0xc0/0xf4 |
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[ 0.048454] [<8108b658>] warn_slowpath_fmt+0x64/0x10c |
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[ 0.048467] [<810bd418>] sched_core_cpu_starting+0x198/0x240 |
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[ 0.048483] [<810c6514>] sched_cpu_starting+0x14/0x80 |
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[ 0.048497] [<8108c0f8>] cpuhp_invoke_callback_range+0x78/0x140 |
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[ 0.048510] [<8108d914>] notify_cpu_starting+0x94/0x140 |
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[ 0.048523] [<8106593c>] start_secondary+0xbc/0x280 |
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[ 0.048539] |
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[ 0.048543] ---[ end trace 0000000000000000 ]--- |
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[ 0.048636] Synchronize counters for CPU 1: done. |
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|
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...for each but CPU 0/boot. |
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Basic debug printks right before the mentioned line say: |
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|
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[ 0.048170] CPU: 1, smt_mask: |
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|
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So smt_mask, which is sibling mask obviously, is empty when entering |
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the function. |
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This is critical, as sched_core_cpu_starting() calculates |
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core-scheduling parameters only once per CPU start, and it's crucial |
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to have all the parameters filled in at that moment (at least it |
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uses cpu_smt_mask() which in fact is `&cpu_sibling_map[cpu]` on |
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MIPS). |
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|
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A bit of debugging led me to that set_cpu_sibling_map() performing |
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the actual map calculation, was being invocated after |
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notify_cpu_start(), and exactly the latter function starts CPU HP |
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callback round (sched_core_cpu_starting() is basically a CPU HP |
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callback). |
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While the flow is same on ARM64 (maps after the notifier, although |
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before calling set_cpu_online()), x86 started calculating sibling |
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maps earlier than starting the CPU HP callbacks in Linux 4.14 (see |
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[0] for the reference). Neither me nor my brief tests couldn't find |
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any potential caveats in calculating the maps right after performing |
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delay calibration, but the WARN splat is now gone. |
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The very same debug prints now yield exactly what I expected from |
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them: |
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|
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[ 0.048433] CPU: 1, smt_mask: 0-1 |
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|
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[0] https://git.kernel.org/pub/scm/linux/kernel/git/mips/linux.git/commit/?id=76ce7cfe35ef |
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|
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Signed-off-by: Alexander Lobakin <alobakin@pm.me> |
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Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> |
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Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de> |
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Signed-off-by: Sasha Levin <sashal@kernel.org> |
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--- |
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arch/mips/kernel/smp.c | 6 +++--- |
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1 file changed, 3 insertions(+), 3 deletions(-) |
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|
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diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c |
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index d542fb7af3ba..1986d1309410 100644 |
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--- a/arch/mips/kernel/smp.c |
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+++ b/arch/mips/kernel/smp.c |
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@@ -351,6 +351,9 @@ asmlinkage void start_secondary(void) |
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cpu = smp_processor_id(); |
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cpu_data[cpu].udelay_val = loops_per_jiffy; |
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|
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+ set_cpu_sibling_map(cpu); |
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+ set_cpu_core_map(cpu); |
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+ |
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cpumask_set_cpu(cpu, &cpu_coherent_mask); |
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notify_cpu_starting(cpu); |
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|
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@@ -362,9 +365,6 @@ asmlinkage void start_secondary(void) |
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/* The CPU is running and counters synchronised, now mark it online */ |
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set_cpu_online(cpu, true); |
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|
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- set_cpu_sibling_map(cpu); |
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- set_cpu_core_map(cpu); |
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- |
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calculate_cpu_foreign_map(); |
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|
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/* |
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-- |
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2.34.1 |
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