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 --- Documentation/ABI/testing/sysfs-class-rc | 137 +++++++++++++++++++++++++++++++ 1 file changed, 137 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-rc (limited to 'Documentation/ABI/testing/sysfs-class-rc') diff --git a/Documentation/ABI/testing/sysfs-class-rc b/Documentation/ABI/testing/sysfs-class-rc new file mode 100644 index 000000000..84e46d70d --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-rc @@ -0,0 +1,137 @@ +What: /sys/class/rc/ +Date: Apr 2010 +KernelVersion: 2.6.35 +Contact: Mauro Carvalho Chehab +Description: + The rc/ class sub-directory belongs to the Remote Controller + core and provides a sysfs interface for configuring infrared + remote controller receivers. + +What: /sys/class/rc/rc/ +Date: Apr 2010 +KernelVersion: 2.6.35 +Contact: Mauro Carvalho Chehab +Description: + A /sys/class/rc/rcN directory is created for each remote + control receiver device where N is the number of the receiver. + +What: /sys/class/rc/rc/protocols +Date: Jun 2010 +KernelVersion: 2.6.36 +Contact: Mauro Carvalho Chehab +Description: + Reading this file returns a list of available protocols, + something like:: + + "rc5 [rc6] nec jvc [sony]" + + Enabled protocols are shown in [] brackets. + + Writing "+proto" will add a protocol to the list of enabled + protocols. + + Writing "-proto" will remove a protocol from the list of enabled + protocols. + + Writing "proto" will enable only "proto". + + Writing "none" will disable all protocols. + + Write fails with EINVAL if an invalid protocol combination or + unknown protocol name is used. + +What: /sys/class/rc/rc/filter +Date: Jan 2014 +KernelVersion: 3.15 +Contact: Mauro Carvalho Chehab +Description: + Sets the scancode filter expected value. + + Use in combination with /sys/class/rc/rcN/filter_mask to set the + expected value of the bits set in the filter mask. + If the hardware supports it then scancodes which do not match + the filter will be ignored. Otherwise the write will fail with + an error. + + This value may be reset to 0 if the current protocol is altered. + +What: /sys/class/rc/rc/filter_mask +Date: Jan 2014 +KernelVersion: 3.15 +Contact: Mauro Carvalho Chehab +Description: + Sets the scancode filter mask of bits to compare. + Use in combination with /sys/class/rc/rcN/filter to set the bits + of the scancode which should be compared against the expected + value. A value of 0 disables the filter to allow all valid + scancodes to be processed. + + If the hardware supports it then scancodes which do not match + the filter will be ignored. Otherwise the write will fail with + an error. + + This value may be reset to 0 if the current protocol is altered. + +What: /sys/class/rc/rc/wakeup_protocols +Date: Feb 2017 +KernelVersion: 4.11 +Contact: Mauro Carvalho Chehab +Description: + Reading this file returns a list of available protocols to use + for the wakeup filter, something like:: + + "rc-5 nec nec-x rc-6-0 rc-6-6a-24 [rc-6-6a-32] rc-6-mce" + + Note that protocol variants are listed, so "nec", "sony", + "rc-5", "rc-6" have their different bit length encodings + listed if available. + + The enabled wakeup protocol is shown in [] brackets. + + Only one protocol can be selected at a time. + + Writing "proto" will use "proto" for wakeup events. + + Writing "none" will disable wakeup. + + Write fails with EINVAL if an invalid protocol combination or + unknown protocol name is used, or if wakeup is not supported by + the hardware. + +What: /sys/class/rc/rc/wakeup_filter +Date: Jan 2014 +KernelVersion: 3.15 +Contact: Mauro Carvalho Chehab +Description: + Sets the scancode wakeup filter expected value. + + Use in combination with /sys/class/rc/rcN/wakeup_filter_mask to + set the expected value of the bits set in the wakeup filter mask + to trigger a system wake event. + + If the hardware supports it and wakeup_filter_mask is not 0 then + scancodes which match the filter will wake the system from e.g. + suspend to RAM or power off. + + Otherwise the write will fail with an error. + + This value may be reset to 0 if the wakeup protocol is altered. + +What: /sys/class/rc/rc/wakeup_filter_mask +Date: Jan 2014 +KernelVersion: 3.15 +Contact: Mauro Carvalho Chehab +Description: + Sets the scancode wakeup filter mask of bits to compare. + + Use in combination with /sys/class/rc/rcN/wakeup_filter to set + the bits of the scancode which should be compared against the + expected value to trigger a system wake event. + + If the hardware supports it and wakeup_filter_mask is not 0 then + scancodes which match the filter will wake the system from e.g. + suspend to RAM or power off. + + Otherwise the write will fail with an error. + + This value may be reset to 0 if the wakeup protocol is altered. -- cgit v1.3.1