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 --- drivers/scsi/ppa.h | 147 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 147 insertions(+) create mode 100644 drivers/scsi/ppa.h (limited to 'drivers/scsi/ppa.h') diff --git a/drivers/scsi/ppa.h b/drivers/scsi/ppa.h new file mode 100644 index 000000000..098bcf7b9 --- /dev/null +++ b/drivers/scsi/ppa.h @@ -0,0 +1,147 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Driver for the PPA3 parallel port SCSI HBA embedded in + * the Iomega ZIP drive + * + * (c) 1996 Grant R. Guenther grant@torque.net + * David Campbell + * + * All comments to David. + */ + +#ifndef _PPA_H +#define _PPA_H + +#define PPA_VERSION "2.07 (for Linux 2.4.x)" + +/* + * this driver has been hacked by Matteo Frigo (athena@theory.lcs.mit.edu) + * to support EPP and scatter-gather. [0.26-athena] + * + * additional hacks by David Campbell + * in response to this driver "mis-behaving" on his machine. + * Fixed EPP to handle "software" changing of EPP port data direction. + * Chased down EPP timeouts + * Made this driver "kernel version friendly" [0.28-athena] + * + * [ Stuff removed ] + * + * Corrected ppa.h for 2.1.x kernels (>=2.1.85) + * Modified "Nat Semi Kludge" for extended chipsets + * [1.41] + * + * Fixed id_probe for EPP 1.9 chipsets (misdetected as EPP 1.7) + * [1.42] + * + * Development solely for 2.1.x kernels from now on! + * [2.00] + * + * Hack and slash at the init code (EPP device check routine) + * Added INSANE option. + * [2.01] + * + * Patch applied to sync against the 2.1.x kernel code + * Included qboot_zip.sh + * [2.02] + * + * Cleaned up the mess left by someone else trying to fix the + * asm section to keep egcc happy. The asm section no longer + * exists, the nibble code is *almost* as fast as the asm code + * providing it is compiled with egcc. + * + * Other clean ups include the follow changes: + * CONFIG_SCSI_PPA_HAVE_PEDANTIC => CONFIG_SCSI_IZIP_EPP16 + * added CONFIG_SCSI_IZIP_SLOW_CTR option + * [2.03] + * + * Use ppa_wait() to check for ready AND connected status bits + * Add ppa_wait() calls to ppa_completion() + * by Peter Cherriman and + * Tim Waugh + * [2.04] + * + * Fix kernel panic on scsi timeout, 2000-08-18 [2.05] + * + * Avoid io_request_lock problems. + * John Cavan [2.06] + * + * Busy wait for connected status bit in ppa_completion() + * in order to cope with some hardware that has this bit low + * for short periods of time. + * Add udelay() to ppa_select() + * by Peter Cherriman and + * Oleg Makarenko + * [2.07] + */ +/* ------ END OF USER CONFIGURABLE PARAMETERS ----- */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +/* batteries not included :-) */ + +/* + * modes in which the driver can operate + */ +#define PPA_AUTODETECT 0 /* Autodetect mode */ +#define PPA_NIBBLE 1 /* work in standard 4 bit mode */ +#define PPA_PS2 2 /* PS/2 byte mode */ +#define PPA_EPP_8 3 /* EPP mode, 8 bit */ +#define PPA_EPP_16 4 /* EPP mode, 16 bit */ +#define PPA_EPP_32 5 /* EPP mode, 32 bit */ +#define PPA_UNKNOWN 6 /* Just in case... */ + +static char *PPA_MODE_STRING[] = +{ + "Autodetect", + "SPP", + "PS/2", + "EPP 8 bit", + "EPP 16 bit", + "EPP 32 bit", + "Unknown"}; + +/* other options */ +#define PPA_BURST_SIZE 512 /* data burst size */ +#define PPA_SELECT_TMO 5000 /* how long to wait for target ? */ +#define PPA_SPIN_TMO 50000 /* ppa_wait loop limiter */ +#define PPA_RECON_TMO 500 /* scsi reconnection loop limiter */ +#define PPA_DEBUG 0 /* debugging option */ +#define IN_EPP_MODE(x) (x == PPA_EPP_8 || x == PPA_EPP_16 || x == PPA_EPP_32) + +/* args to ppa_connect */ +#define CONNECT_EPP_MAYBE 1 +#define CONNECT_NORMAL 0 + +#define r_dtr(x) (unsigned char)inb((x)) +#define r_str(x) (unsigned char)inb((x)+1) +#define r_ctr(x) (unsigned char)inb((x)+2) +#define r_epp(x) (unsigned char)inb((x)+4) +#define r_fifo(x) (unsigned char)inb((x)) /* x must be base_hi */ + /* On PCI is base+0x400 != base_hi */ +#define r_ecr(x) (unsigned char)inb((x)+0x2) /* x must be base_hi */ + +#define w_dtr(x,y) outb(y, (x)) +#define w_str(x,y) outb(y, (x)+1) +#define w_epp(x,y) outb(y, (x)+4) +#define w_fifo(x,y) outb(y, (x)) /* x must be base_hi */ +#define w_ecr(x,y) outb(y, (x)+0x2)/* x must be base_hi */ + +#ifdef CONFIG_SCSI_IZIP_SLOW_CTR +#define w_ctr(x,y) outb_p(y, (x)+2) +#else +#define w_ctr(x,y) outb(y, (x)+2) +#endif + +static int ppa_engine(ppa_struct *, struct scsi_cmnd *); + +#endif /* _PPA_H */ -- cgit v1.3.1