From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- scripts/kconfig/tests/transitional/Kconfig | 132 +++++++++++++++++++++ scripts/kconfig/tests/transitional/__init__.py | 25 ++++ scripts/kconfig/tests/transitional/expected_config | 15 +++ scripts/kconfig/tests/transitional/expected_stdout | 1 + scripts/kconfig/tests/transitional/initial_config | 20 ++++ 5 files changed, 193 insertions(+) create mode 100644 scripts/kconfig/tests/transitional/Kconfig create mode 100644 scripts/kconfig/tests/transitional/__init__.py create mode 100644 scripts/kconfig/tests/transitional/expected_config create mode 100644 scripts/kconfig/tests/transitional/expected_stdout create mode 100644 scripts/kconfig/tests/transitional/initial_config (limited to 'scripts/kconfig/tests/transitional') diff --git a/scripts/kconfig/tests/transitional/Kconfig b/scripts/kconfig/tests/transitional/Kconfig new file mode 100644 index 000000000..faa4d396f --- /dev/null +++ b/scripts/kconfig/tests/transitional/Kconfig @@ -0,0 +1,132 @@ +# SPDX-License-Identifier: GPL-2.0 +# Test transitional symbols for config migration with all Kconfig types + +# Enable module support for tristate testing +config MODULES + bool "Enable loadable module support" + modules + default y + +# Basic migration tests for all types +config NEW_BOOL + bool "New bool option" + default OLD_BOOL + +config OLD_BOOL + bool + transitional + +config NEW_TRISTATE + tristate "New tristate option" + default OLD_TRISTATE + +config OLD_TRISTATE + tristate + transitional + +config NEW_STRING + string "New string option" + default OLD_STRING + +config OLD_STRING + string + transitional + +config NEW_HEX + hex "New hex option" + default OLD_HEX + +config OLD_HEX + hex + transitional + +config NEW_INT + int "New int option" + default OLD_INT + +config OLD_INT + int + transitional + +# Precedence tests for all types +config NEW_BOOL_PRECEDENCE + bool "New bool option with precedence" + default OLD_BOOL_PRECEDENCE + +config OLD_BOOL_PRECEDENCE + bool + transitional + +config NEW_STRING_PRECEDENCE + string "New string option with precedence" + default OLD_STRING_PRECEDENCE + +config OLD_STRING_PRECEDENCE + string + transitional + +config NEW_TRISTATE_PRECEDENCE + tristate "New tristate option with precedence" + default OLD_TRISTATE_PRECEDENCE + +config OLD_TRISTATE_PRECEDENCE + tristate + transitional + +config NEW_HEX_PRECEDENCE + hex "New hex option with precedence" + default OLD_HEX_PRECEDENCE + +config OLD_HEX_PRECEDENCE + hex + transitional + +config NEW_INT_PRECEDENCE + int "New int option with precedence" + default OLD_INT_PRECEDENCE + +config OLD_INT_PRECEDENCE + int + transitional + +# Test that help sections are allowed for transitional symbols +config OLD_WITH_HELP + bool + transitional + help + This transitional symbol has a help section to validate that help is allowed. + +# Test that we can set something to =n via transitional symbol +config NEW_DISABLED + tristate "Check for setting to disabled" + default OLD_DISABLED + +config OLD_DISABLED + tristate + transitional + +# Test that a potential new value disappears if it lacks a prompt +config NEW_DISABLED_UNSAVED + tristate + default OLD_DISABLED + +config OLD_DISABLED_UNSAVED + tristate + transitional + +# Test conditional default: transitional value should not prevent prompting +# when default visibility makes the expression evaluate to 'no' +config DEPENDENCY_TEST + bool "Dependency for testing" + default n + +config NEW_CONDITIONAL_DEFAULT + bool "New option with conditional default" + default OLD_CONDITIONAL_DEFAULT if DEPENDENCY_TEST + +config OLD_CONDITIONAL_DEFAULT + bool + transitional + +config REGULAR_OPTION + bool "Regular option" diff --git a/scripts/kconfig/tests/transitional/__init__.py b/scripts/kconfig/tests/transitional/__init__.py new file mode 100644 index 000000000..b50ba2397 --- /dev/null +++ b/scripts/kconfig/tests/transitional/__init__.py @@ -0,0 +1,25 @@ +# SPDX-License-Identifier: GPL-2.0 +""" +Test transitional symbol migration functionality for all Kconfig types. + +This tests that: +- OLD_* options in existing .config cause NEW_* options to be set +- OLD_* options are not written to the new .config file +- NEW_* options appear in the new .config file with correct values +- NEW_* options with defaults from transitional symbols are not prompted +- All Kconfig types work correctly: bool, tristate, string, hex, int +- User-set NEW values take precedence over conflicting OLD transitional values +""" + +def test(conf): + # Run olddefconfig to process the migration with the initial config + assert conf.olddefconfig(dot_config='initial_config') == 0 + + # Check that the configuration matches expected output + assert conf.config_contains('expected_config') + + # Test oldconfig to ensure symbols with transitional defaults are not prompted + assert conf.oldconfig(dot_config='initial_config', in_keys='n\n') == 0 + + # Except for when conditional default evaluates to 'no' + assert conf.stdout_contains('expected_stdout') diff --git a/scripts/kconfig/tests/transitional/expected_config b/scripts/kconfig/tests/transitional/expected_config new file mode 100644 index 000000000..e01f5f070 --- /dev/null +++ b/scripts/kconfig/tests/transitional/expected_config @@ -0,0 +1,15 @@ +CONFIG_MODULES=y +CONFIG_NEW_BOOL=y +CONFIG_NEW_TRISTATE=m +CONFIG_NEW_STRING="test string" +CONFIG_NEW_HEX=0x1234 +CONFIG_NEW_INT=42 +# CONFIG_NEW_BOOL_PRECEDENCE is not set +CONFIG_NEW_STRING_PRECEDENCE="user value" +CONFIG_NEW_TRISTATE_PRECEDENCE=y +CONFIG_NEW_HEX_PRECEDENCE=0xABCD +CONFIG_NEW_INT_PRECEDENCE=100 +# CONFIG_NEW_DISABLED is not set +# CONFIG_DEPENDENCY_TEST is not set +# CONFIG_NEW_CONDITIONAL_DEFAULT is not set +# CONFIG_REGULAR_OPTION is not set diff --git a/scripts/kconfig/tests/transitional/expected_stdout b/scripts/kconfig/tests/transitional/expected_stdout new file mode 100644 index 000000000..6f0b285d6 --- /dev/null +++ b/scripts/kconfig/tests/transitional/expected_stdout @@ -0,0 +1 @@ +New option with conditional default (NEW_CONDITIONAL_DEFAULT) [N/y/?] (NEW) n diff --git a/scripts/kconfig/tests/transitional/initial_config b/scripts/kconfig/tests/transitional/initial_config new file mode 100644 index 000000000..68b7da672 --- /dev/null +++ b/scripts/kconfig/tests/transitional/initial_config @@ -0,0 +1,20 @@ +CONFIG_MODULES=y +CONFIG_OLD_BOOL=y +CONFIG_OLD_TRISTATE=m +CONFIG_OLD_STRING="test string" +CONFIG_OLD_HEX=0x1234 +CONFIG_OLD_INT=42 +# CONFIG_NEW_BOOL_PRECEDENCE is not set +CONFIG_OLD_BOOL_PRECEDENCE=y +CONFIG_NEW_STRING_PRECEDENCE="user value" +CONFIG_OLD_STRING_PRECEDENCE="old value" +CONFIG_NEW_TRISTATE_PRECEDENCE=y +CONFIG_OLD_TRISTATE_PRECEDENCE=m +CONFIG_NEW_HEX_PRECEDENCE=0xABCD +CONFIG_OLD_HEX_PRECEDENCE=0x5678 +CONFIG_NEW_INT_PRECEDENCE=100 +CONFIG_OLD_INT_PRECEDENCE=200 +# CONFIG_OLD_DISABLED is not set +# CONFIG_OLD_DISABLED_UNSAVED is not set +# CONFIG_DEPENDENCY_TEST is not set +CONFIG_OLD_CONDITIONAL_DEFAULT=y -- cgit v1.3.1