kernel: disable CONFIG_RCU_EXPERT and friends

Based on the existing documentation [1][2], I dare anyone to demonstrate that
we need to fine-tune these RCU parameters. The (performance) breakage potential
for doing so is immense, so let's just please put down this loaded footgun.

Disable CONFIG_RCU_EXPERT and its dependent symbols. Additionally, remove the
CONFIG_RCU_EXPERT symbol from the target kconfigs which contain it.

[1] https://www.kernel.org/doc/Documentation/RCU/Design/Data-Structures/Data-Structures.html
[2] https://lwn.net/Articles/777214/

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>

14 files changed, 2 insertions, 23 deletions

diff --git a/target/linux/gemini/config-5.10 b/target/linux/gemini/config-5.10
index 2382e85bea9..37a7b16a25b 100644
--- a/target/linux/gemini/config-5.10
+++ b/target/linux/gemini/config-5.10
@@ -333,7 +333,6 @@ CONFIG_PREEMPT_RCU=y
 CONFIG_PROC_PAGE_MONITOR=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RD_BZIP2=y
diff --git a/target/linux/gemini/config-5.4 b/target/linux/gemini/config-5.4
index 9d84571b3cf..702810413c6 100644
--- a/target/linux/gemini/config-5.4
+++ b/target/linux/gemini/config-5.4
@@ -369,7 +369,6 @@ CONFIG_PREEMPT_RCU=y
 CONFIG_PROC_PAGE_MONITOR=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RD_BZIP2=y
diff --git a/target/linux/generic/config-5.10 b/target/linux/generic/config-5.10
index f944f1718fa..91f137fbc3a 100644
--- a/target/linux/generic/config-5.10
+++ b/target/linux/generic/config-5.10
@@ -4631,12 +4631,8 @@ CONFIG_PWRSEQ_SIMPLE=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=60
 # CONFIG_RCU_EQS_DEBUG is not set
 # CONFIG_RCU_EXPEDITE_BOOT is not set
-CONFIG_RCU_EXPERT=y
-CONFIG_RCU_FANOUT=32
-CONFIG_RCU_FANOUT_LEAF=16
-# CONFIG_RCU_FAST_NO_HZ is not set
+# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_KTHREAD_PRIO=0
-# CONFIG_RCU_NOCB_CPU is not set
 # CONFIG_RCU_PERF_TEST is not set
 # CONFIG_RCU_REF_SCALE_TEST is not set
 # CONFIG_RCU_SCALE_TEST is not set
@@ -5995,7 +5991,6 @@ CONFIG_SYSVIPC_SYSCTL=y
 # CONFIG_TARGET_CORE is not set
 # CONFIG_TASKSTATS is not set
 # CONFIG_TASKS_RCU is not set
-CONFIG_TASKS_TRACE_RCU_READ_MB=y
 # CONFIG_TASK_XACCT is not set
 # CONFIG_TC35815 is not set
 # CONFIG_TCG_ATMEL is not set
diff --git a/target/linux/generic/config-5.4 b/target/linux/generic/config-5.4
index 45d8f0976e4..06f5e43a6dd 100644
--- a/target/linux/generic/config-5.4
+++ b/target/linux/generic/config-5.4
@@ -4262,12 +4262,8 @@ CONFIG_PWRSEQ_SIMPLE=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=60
 # CONFIG_RCU_EQS_DEBUG is not set
 # CONFIG_RCU_EXPEDITE_BOOT is not set
-CONFIG_RCU_EXPERT=y
-CONFIG_RCU_FANOUT=32
-CONFIG_RCU_FANOUT_LEAF=16
-# CONFIG_RCU_FAST_NO_HZ is not set
+# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_KTHREAD_PRIO=0
-# CONFIG_RCU_NOCB_CPU is not set
 # CONFIG_RCU_PERF_TEST is not set
 # CONFIG_RCU_TORTURE_TEST is not set
 CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY=3
diff --git a/target/linux/ipq807x/config-default b/target/linux/ipq807x/config-default
index 94acb8672de..fc77a4995bd 100644
--- a/target/linux/ipq807x/config-default
+++ b/target/linux/ipq807x/config-default
@@ -531,7 +531,6 @@ CONFIG_QUEUED_SPINLOCKS=y
 # CONFIG_RANDOMIZE_BASE is not set
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RD_GZIP=y
diff --git a/target/linux/layerscape/armv7/config-5.4 b/target/linux/layerscape/armv7/config-5.4
index 54ac6a41522..126402d76cd 100644
--- a/target/linux/layerscape/armv7/config-5.4
+++ b/target/linux/layerscape/armv7/config-5.4
@@ -505,7 +505,6 @@ CONFIG_QORIQ_CPUFREQ=y
 CONFIG_RAS=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RD_BZIP2=y
diff --git a/target/linux/layerscape/armv8_64b/config-5.4 b/target/linux/layerscape/armv8_64b/config-5.4
index 2ab42c9d709..6846fc96aa4 100644
--- a/target/linux/layerscape/armv8_64b/config-5.4
+++ b/target/linux/layerscape/armv8_64b/config-5.4
@@ -671,7 +671,6 @@ CONFIG_RAID6_PQ=y
 CONFIG_RAS=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RD_BZIP2=y
diff --git a/target/linux/mediatek/mt7623/config-5.10 b/target/linux/mediatek/mt7623/config-5.10
index 95cad157669..042f055bb23 100644
--- a/target/linux/mediatek/mt7623/config-5.10
+++ b/target/linux/mediatek/mt7623/config-5.10
@@ -509,7 +509,6 @@ CONFIG_PWM_SYSFS=y
 CONFIG_RAS=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_REGMAP=y
diff --git a/target/linux/oxnas/ox810se/config-default b/target/linux/oxnas/ox810se/config-default
index 137b32a070e..4d5e50cd244 100644
--- a/target/linux/oxnas/ox810se/config-default
+++ b/target/linux/oxnas/ox810se/config-default
@@ -6,6 +6,5 @@ CONFIG_CPU_IDLE_MULTIPLE_DRIVERS=y
 CONFIG_EXT4_FS=y
 CONFIG_FS_MBCACHE=y
 CONFIG_MACH_OX810SE=y
-# CONFIG_RCU_EXPERT is not set
 # CONFIG_RCU_NEED_SEGCBLIST is not set
 # CONFIG_RCU_STALL_COMMON is not set
diff --git a/target/linux/oxnas/ox820/config-default b/target/linux/oxnas/ox820/config-default
index b846b6ed8fc..269eb2c380c 100644
--- a/target/linux/oxnas/ox820/config-default
+++ b/target/linux/oxnas/ox820/config-default
@@ -79,7 +79,6 @@ CONFIG_PCI_MSI_IRQ_DOMAIN=y
 # CONFIG_PL310_ERRATA_769419 is not set
 CONFIG_PM_SLEEP_SMP=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RFS_ACCEL=y
diff --git a/target/linux/rockchip/armv8/config-5.10 b/target/linux/rockchip/armv8/config-5.10
index 3b03333af08..36a3cefaf1e 100644
--- a/target/linux/rockchip/armv8/config-5.10
+++ b/target/linux/rockchip/armv8/config-5.10
@@ -483,7 +483,6 @@ CONFIG_RAS=y
 CONFIG_RATIONAL=y
 # CONFIG_RAVE_SP_CORE is not set
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RCU_TRACE=y
diff --git a/target/linux/rockchip/armv8/config-5.4 b/target/linux/rockchip/armv8/config-5.4
index d3c2cd985aa..0a2575adbfd 100644
--- a/target/linux/rockchip/armv8/config-5.4
+++ b/target/linux/rockchip/armv8/config-5.4
@@ -463,7 +463,6 @@ CONFIG_RAS=y
 CONFIG_RATIONAL=y
 # CONFIG_RAVE_SP_CORE is not set
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_RCU_TRACE=y
diff --git a/target/linux/tegra/config-5.10 b/target/linux/tegra/config-5.10
index a99ff204479..89d318952a0 100644
--- a/target/linux/tegra/config-5.10
+++ b/target/linux/tegra/config-5.10
@@ -350,7 +350,6 @@ CONFIG_PWM_TEGRA=y
 CONFIG_RAS=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_REGMAP=y
diff --git a/target/linux/tegra/config-5.4 b/target/linux/tegra/config-5.4
index c2868fedbee..ce421e151a4 100644
--- a/target/linux/tegra/config-5.4
+++ b/target/linux/tegra/config-5.4
@@ -343,7 +343,6 @@ CONFIG_PWM_TEGRA=y
 CONFIG_RAS=y
 CONFIG_RATIONAL=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=21
-# CONFIG_RCU_EXPERT is not set
 CONFIG_RCU_NEED_SEGCBLIST=y
 CONFIG_RCU_STALL_COMMON=y
 CONFIG_REFCOUNT_FULL=y