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 --- arch/m68k/Kconfig.debug | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 arch/m68k/Kconfig.debug (limited to 'arch/m68k/Kconfig.debug') diff --git a/arch/m68k/Kconfig.debug b/arch/m68k/Kconfig.debug new file mode 100644 index 000000000..d036f9038 --- /dev/null +++ b/arch/m68k/Kconfig.debug @@ -0,0 +1,45 @@ +# SPDX-License-Identifier: GPL-2.0 + +config BOOTPARAM + bool "Compiled-in Kernel Boot Parameter" + +config BOOTPARAM_STRING + string "Kernel Boot Parameter" + default "console=ttyS0,19200" + depends on BOOTPARAM + +config EARLY_PRINTK + bool "Early printk" + depends on MMU_MOTOROLA + help + Write kernel log output directly to a serial port. + Where implemented, output goes to the framebuffer as well. + PROM console functionality on Sun 3x is not affected by this option. + + Pass "earlyprintk" on the kernel command line to get a + boot console. + + This is useful for kernel debugging when your machine crashes very + early, i.e. before the normal console driver is loaded. + You should normally say N here, unless you want to debug such a crash. + +if !MMU + +config FULLDEBUG + bool "Full Symbolic/Source Debugging support" + help + Enable debugging symbols on kernel build. + +config HIGHPROFILE + bool "Use fast second timer for profiling" + depends on COLDFIRE + help + Use a fast secondary clock to produce profiling information. + +config BDM_DISABLE + bool "Disable BDM signals" + depends on COLDFIRE + help + Disable the ColdFire CPU's BDM signals. + +endif -- cgit v1.3.1