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/usb/gadget/usbstring.c | 91 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 drivers/usb/gadget/usbstring.c (limited to 'drivers/usb/gadget/usbstring.c') diff --git a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c new file mode 100644 index 000000000..37a2f1b61 --- /dev/null +++ b/drivers/usb/gadget/usbstring.c @@ -0,0 +1,91 @@ +// SPDX-License-Identifier: LGPL-2.1+ +/* + * Copyright (C) 2003 David Brownell + */ + +#include +#include +#include +#include +#include +#include +#include + +#include +#include + + +/** + * usb_gadget_get_string - fill out a string descriptor + * @table: of c strings encoded using UTF-8 + * @id: string id, from low byte of wValue in get string descriptor + * @buf: at least 256 bytes, must be 16-bit aligned + * + * Finds the UTF-8 string matching the ID, and converts it into a + * string descriptor in utf16-le. + * Returns length of descriptor (always even) or negative errno + * + * If your driver needs stings in multiple languages, you'll probably + * "switch (wIndex) { ... }" in your ep0 string descriptor logic, + * using this routine after choosing which set of UTF-8 strings to use. + * Note that US-ASCII is a strict subset of UTF-8; any string bytes with + * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1 + * characters (which are also widely used in C strings). + */ +int +usb_gadget_get_string (const struct usb_gadget_strings *table, int id, u8 *buf) +{ + struct usb_string *s; + int len; + + /* descriptor 0 has the language id */ + if (id == 0) { + buf [0] = 4; + buf [1] = USB_DT_STRING; + buf [2] = (u8) table->language; + buf [3] = (u8) (table->language >> 8); + return 4; + } + for (s = table->strings; s && s->s; s++) + if (s->id == id) + break; + + /* unrecognized: stall. */ + if (!s || !s->s) + return -EINVAL; + + /* string descriptors have length, tag, then UTF16-LE text */ + len = min_t(size_t, USB_MAX_STRING_LEN, strlen(s->s)); + len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN, + (wchar_t *) &buf[2], USB_MAX_STRING_LEN); + if (len < 0) + return -EINVAL; + buf [0] = (len + 1) * 2; + buf [1] = USB_DT_STRING; + return buf [0]; +} +EXPORT_SYMBOL_GPL(usb_gadget_get_string); + +/** + * usb_validate_langid - validate usb language identifiers + * @langid: usb language identifier + * + * Returns true for valid language identifier, otherwise false. + */ +bool usb_validate_langid(u16 langid) +{ + u16 primary_lang = langid & 0x3ff; /* bit [9:0] */ + u16 sub_lang = langid >> 10; /* bit [15:10] */ + + switch (primary_lang) { + case 0: + case 0x62 ... 0xfe: + case 0x100 ... 0x3ff: + return false; + } + if (!sub_lang) + return false; + + return true; +} +EXPORT_SYMBOL_GPL(usb_validate_langid); -- cgit v1.3.1