sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

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 <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

2 files changed, 49 insertions, 0 deletions

diff --git a/Documentation/driver-api/xilinx/eemi.rst b/Documentation/driver-api/xilinx/eemi.rst
new file mode 100644
index 000000000..c1bc47b90
--- /dev/null
+++ b/Documentation/driver-api/xilinx/eemi.rst
@@ -0,0 +1,40 @@
+====================================
+Xilinx Zynq MPSoC EEMI Documentation
+====================================
+
+Xilinx Zynq MPSoC Firmware Interface
+-------------------------------------
+The zynqmp-firmware node describes the interface to platform firmware.
+ZynqMP has an interface to communicate with secure firmware. Firmware
+driver provides an interface to firmware APIs. Interface APIs can be
+used by any driver to communicate with PMC(Platform Management Controller).
+
+Embedded Energy Management Interface (EEMI)
+----------------------------------------------
+The embedded energy management interface is used to allow software
+components running across different processing clusters on a chip or
+device to communicate with a power management controller (PMC) on a
+device to issue or respond to power management requests.
+
+Any driver who wants to communicate with PMC using EEMI APIs use the
+functions provided for each function.
+
+IOCTL
+------
+IOCTL API is for device control and configuration. It is not a system
+IOCTL but it is an EEMI API. This API can be used by master to control
+any device specific configuration. IOCTL definitions can be platform
+specific. This API also manage shared device configuration.
+
+The following IOCTL IDs are valid for device control:
+- IOCTL_SET_PLL_FRAC_MODE	8
+- IOCTL_GET_PLL_FRAC_MODE	9
+- IOCTL_SET_PLL_FRAC_DATA	10
+- IOCTL_GET_PLL_FRAC_DATA	11
+
+Refer EEMI API guide [0] for IOCTL specific parameters and other EEMI APIs.
+
+References
+----------
+[0] Embedded Energy Management Interface (EEMI) API guide:
+    https://www.xilinx.com/support/documentation/user_guides/ug1200-eemi-api.pdf
diff --git a/Documentation/driver-api/xilinx/index.rst b/Documentation/driver-api/xilinx/index.rst
new file mode 100644
index 000000000..c95bda55d
--- /dev/null
+++ b/Documentation/driver-api/xilinx/index.rst
@@ -0,0 +1,9 @@
+
+===========
+Xilinx FPGA
+===========
+
+.. toctree::
+    :maxdepth: 1
+
+    eemi