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/debugfs-wilco-ec | 45 ++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 Documentation/ABI/testing/debugfs-wilco-ec (limited to 'Documentation/ABI/testing/debugfs-wilco-ec') diff --git a/Documentation/ABI/testing/debugfs-wilco-ec b/Documentation/ABI/testing/debugfs-wilco-ec new file mode 100644 index 000000000..682e3c09e --- /dev/null +++ b/Documentation/ABI/testing/debugfs-wilco-ec @@ -0,0 +1,45 @@ +What: /sys/kernel/debug/wilco_ec/h1_gpio +Date: April 2019 +KernelVersion: 5.2 +Description: + As part of Chrome OS's FAFT (Fully Automated Firmware Testing) + tests, we need to ensure that the H1 chip is properly setting + some GPIO lines. The h1_gpio attribute exposes the state + of the lines: + - ENTRY_TO_FACT_MODE in BIT(0) + - SPI_CHROME_SEL in BIT(1) + + Output will formatted with "0x%02x\n". + +What: /sys/kernel/debug/wilco_ec/raw +Date: January 2019 +KernelVersion: 5.1 +Description: + Write and read raw mailbox commands to the EC. + + You can write a hexadecimal sentence to raw, and that series of + bytes will be sent to the EC. Then, you can read the bytes of + response by reading from raw. + + For writing, bytes 0-1 indicate the message type, one of enum + wilco_ec_msg_type. Byte 2+ consist of the data passed in the + request, starting at MBOX[0]. At least three bytes are required + for writing, two for the type and at least a single byte of + data. + + Example:: + + // Request EC info type 3 (EC firmware build date) + // Corresponds with sending type 0x00f0 with + // MBOX = [38, 00, 03, 00] + $ echo 00 f0 38 00 03 00 > /sys/kernel/debug/wilco_ec/raw + // View the result. The decoded ASCII result "12/21/18" is + // included after the raw hex. + // Corresponds with MBOX = [00, 00, 31, 32, 2f, 32, 31, 38, ...] + $ cat /sys/kernel/debug/wilco_ec/raw + 00 00 31 32 2f 32 31 2f 31 38 00 38 00 01 00 2f 00 ..12/21/18.8... + + Note that the first 16 bytes of the received MBOX[] will be + printed, even if some of the data is junk, and skipping bytes + 17 to 32. It is up to you to know how many of the first bytes of + data are the actual response. -- cgit v1.3.1