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/net/usb/plusb.c | 153 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 153 insertions(+) create mode 100644 drivers/net/usb/plusb.c (limited to 'drivers/net/usb/plusb.c') diff --git a/drivers/net/usb/plusb.c b/drivers/net/usb/plusb.c new file mode 100644 index 000000000..289411485 --- /dev/null +++ b/drivers/net/usb/plusb.c @@ -0,0 +1,153 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * PL-2301/2302 USB host-to-host link cables + * Copyright (C) 2000-2005 by David Brownell + */ + +// #define DEBUG // error path messages, extra info +// #define VERBOSE // more; success messages + +#include +#include +#include +#include +#include +#include +#include +#include + + +/* + * Prolific PL-2301/PL-2302 driver ... http://www.prolific.com.tw/ + * + * The protocol and handshaking used here should be bug-compatible + * with the Linux 2.2 "plusb" driver, by Deti Fliegl. + * + * HEADS UP: this handshaking isn't all that robust. This driver + * gets confused easily if you unplug one end of the cable then + * try to connect it again; you'll need to restart both ends. The + * "naplink" software (used by some PlayStation/2 developers) does + * the handshaking much better! Also, sometimes this hardware + * seems to get wedged under load. Prolific docs are weak, and + * don't identify differences between PL2301 and PL2302, much less + * anything to explain the different PL2302 versions observed. + * + * NOTE: pl2501 has several modes, including pl2301 and pl2302 + * compatibility. Some docs suggest the difference between 2301 + * and 2302 is only to make MS-Windows use a different driver... + * + * pl25a1 glue based on patch from Tony Gibbs. Prolific "docs" on + * this chip are as usual incomplete about what control messages + * are supported. + */ + +/* + * Bits 0-4 can be used for software handshaking; they're set from + * one end, cleared from the other, "read" with the interrupt byte. + */ +#define PL_S_EN (1<<7) /* (feature only) suspend enable */ +/* reserved bit -- rx ready (6) ? */ +#define PL_TX_READY (1<<5) /* (interrupt only) transmit ready */ +#define PL_RESET_OUT (1<<4) /* reset output pipe */ +#define PL_RESET_IN (1<<3) /* reset input pipe */ +#define PL_TX_C (1<<2) /* transmission complete */ +#define PL_TX_REQ (1<<1) /* transmission received */ +#define PL_PEER_E (1<<0) /* peer exists */ + +static inline int +pl_vendor_req(struct usbnet *dev, u8 req, u8 val, u8 index) +{ + return usbnet_write_cmd(dev, req, USB_TYPE_VENDOR | USB_RECIP_DEVICE, + val, index, NULL, 0); +} + +static inline int +pl_set_QuickLink_features(struct usbnet *dev, int val) +{ + return pl_vendor_req(dev, 3, (u8) val, 0); +} + +static int pl_reset(struct usbnet *dev) +{ + int status; + + /* some units seem to need this reset, others reject it utterly. + * FIXME be more like "naplink" or windows drivers. + */ + status = pl_set_QuickLink_features(dev, + PL_S_EN|PL_RESET_OUT|PL_RESET_IN|PL_PEER_E); + if (status != 0 && netif_msg_probe(dev)) + netif_dbg(dev, link, dev->net, "pl_reset --> %d\n", status); + return 0; +} + +static const struct driver_info prolific_info = { + .description = "Prolific PL-2301/PL-2302/PL-25A1/PL-27A1", + .flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT, + /* some PL-2302 versions seem to fail usb_set_interface() */ + .reset = pl_reset, +}; + + +/*-------------------------------------------------------------------------*/ + +/* + * Proilific's name won't normally be on the cables, and + * may not be on the device. + */ + +static const struct usb_device_id products [] = { + +/* full speed cables */ +{ + USB_DEVICE(0x067b, 0x0000), // PL-2301 + .driver_info = (unsigned long) &prolific_info, +}, { + USB_DEVICE(0x067b, 0x0001), // PL-2302 + .driver_info = (unsigned long) &prolific_info, +}, + +/* high speed cables */ +{ + USB_DEVICE(0x067b, 0x25a1), /* PL-25A1, no eeprom */ + .driver_info = (unsigned long) &prolific_info, +}, { + USB_DEVICE(0x050d, 0x258a), /* Belkin F5U258/F5U279 (PL-25A1) */ + .driver_info = (unsigned long) &prolific_info, +}, { + USB_DEVICE(0x3923, 0x7825), /* National Instruments USB + * Host-to-Host Cable + */ + .driver_info = (unsigned long) &prolific_info, + +}, + +/* super speed cables */ +{ + USB_DEVICE(0x067b, 0x27a1), /* PL-27A1, no eeprom + * also: goobay Active USB 3.0 + * Data Link, + * Unitek Y-3501 + */ + .driver_info = (unsigned long) &prolific_info, +}, + + { }, // END +}; +MODULE_DEVICE_TABLE(usb, products); + +static struct usb_driver plusb_driver = { + .name = "plusb", + .id_table = products, + .probe = usbnet_probe, + .disconnect = usbnet_disconnect, + .suspend = usbnet_suspend, + .resume = usbnet_resume, + .disable_hub_initiated_lpm = 1, +}; + +module_usb_driver(plusb_driver); + +MODULE_AUTHOR("David Brownell"); +MODULE_DESCRIPTION("Prolific PL-2301/2302/25A1/27A1 USB Host to Host Link Driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1