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 --- arch/alpha/lib/memmove.S | 183 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 183 insertions(+) create mode 100644 arch/alpha/lib/memmove.S (limited to 'arch/alpha/lib/memmove.S') diff --git a/arch/alpha/lib/memmove.S b/arch/alpha/lib/memmove.S new file mode 100644 index 000000000..3a27689e3 --- /dev/null +++ b/arch/alpha/lib/memmove.S @@ -0,0 +1,183 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/lib/memmove.S + * + * Barely optimized memmove routine for Alpha EV5. + * + * This is hand-massaged output from the original memcpy.c. We defer to + * memcpy whenever possible; the backwards copy loops are not unrolled. + */ +#include + .set noat + .set noreorder + .text + + .align 4 + .globl memmove + .ent memmove +memmove: + ldgp $29, 0($27) + unop + nop + .prologue 1 + + addq $16,$18,$4 + addq $17,$18,$5 + cmpule $4,$17,$1 /* dest + n <= src */ + cmpule $5,$16,$2 /* dest >= src + n */ + + bis $1,$2,$1 + mov $16,$0 + xor $16,$17,$2 + bne $1,memcpy !samegp + + and $2,7,$2 /* Test for src/dest co-alignment. */ + and $16,7,$1 + cmpule $16,$17,$3 + bne $3,$memmove_up /* dest < src */ + + and $4,7,$1 + bne $2,$misaligned_dn + unop + beq $1,$skip_aligned_byte_loop_head_dn + +$aligned_byte_loop_head_dn: + lda $4,-1($4) + lda $5,-1($5) + unop + ble $18,$egress + + ldq_u $3,0($5) + ldq_u $2,0($4) + lda $18,-1($18) + extbl $3,$5,$1 + + insbl $1,$4,$1 + mskbl $2,$4,$2 + bis $1,$2,$1 + and $4,7,$6 + + stq_u $1,0($4) + bne $6,$aligned_byte_loop_head_dn + +$skip_aligned_byte_loop_head_dn: + lda $18,-8($18) + blt $18,$skip_aligned_word_loop_dn + +$aligned_word_loop_dn: + ldq $1,-8($5) + nop + lda $5,-8($5) + lda $18,-8($18) + + stq $1,-8($4) + nop + lda $4,-8($4) + bge $18,$aligned_word_loop_dn + +$skip_aligned_word_loop_dn: + lda $18,8($18) + bgt $18,$byte_loop_tail_dn + unop + ret $31,($26),1 + + .align 4 +$misaligned_dn: + nop + fnop + unop + beq $18,$egress + +$byte_loop_tail_dn: + ldq_u $3,-1($5) + ldq_u $2,-1($4) + lda $5,-1($5) + lda $4,-1($4) + + lda $18,-1($18) + extbl $3,$5,$1 + insbl $1,$4,$1 + mskbl $2,$4,$2 + + bis $1,$2,$1 + stq_u $1,0($4) + bgt $18,$byte_loop_tail_dn + br $egress + +$memmove_up: + mov $16,$4 + mov $17,$5 + bne $2,$misaligned_up + beq $1,$skip_aligned_byte_loop_head_up + +$aligned_byte_loop_head_up: + unop + ble $18,$egress + ldq_u $3,0($5) + ldq_u $2,0($4) + + lda $18,-1($18) + extbl $3,$5,$1 + insbl $1,$4,$1 + mskbl $2,$4,$2 + + bis $1,$2,$1 + lda $5,1($5) + stq_u $1,0($4) + lda $4,1($4) + + and $4,7,$6 + bne $6,$aligned_byte_loop_head_up + +$skip_aligned_byte_loop_head_up: + lda $18,-8($18) + blt $18,$skip_aligned_word_loop_up + +$aligned_word_loop_up: + ldq $1,0($5) + nop + lda $5,8($5) + lda $18,-8($18) + + stq $1,0($4) + nop + lda $4,8($4) + bge $18,$aligned_word_loop_up + +$skip_aligned_word_loop_up: + lda $18,8($18) + bgt $18,$byte_loop_tail_up + unop + ret $31,($26),1 + + .align 4 +$misaligned_up: + nop + fnop + unop + beq $18,$egress + +$byte_loop_tail_up: + ldq_u $3,0($5) + ldq_u $2,0($4) + lda $18,-1($18) + extbl $3,$5,$1 + + insbl $1,$4,$1 + mskbl $2,$4,$2 + bis $1,$2,$1 + stq_u $1,0($4) + + lda $5,1($5) + lda $4,1($4) + nop + bgt $18,$byte_loop_tail_up + +$egress: + ret $31,($26),1 + nop + nop + nop + + .end memmove + EXPORT_SYMBOL(memmove) -- cgit v1.3.1