riscv: qspinlock: Introduce combo spinlock
Combo spinlock could support queued and ticket in one Linux Image and select them during boot time via errata mechanism. Here is the func size (Bytes) comparison table below: TYPE : COMBO | TICKET | QUEUED arch_spin_lock : 106 | 60 | 50 arch_spin_unlock : 54 | 36 | 26 arch_spin_trylock : 110 | 72 | 54 arch_spin_is_locked : 48 | 34 | 20 arch_spin_is_contended : 56 | 40 | 24 rch_spin_value_unlocked : 48 | 34 | 24 One example of disassemble combo arch_spin_unlock: 0xffffffff8000409c <+14>: nop # detour slot 0xffffffff800040a0 <+18>: fence rw,w # queued spinlock start 0xffffffff800040a4 <+22>: sb zero,0(a4) # queued spinlock end 0xffffffff800040a8 <+26>: ld s0,8(sp) 0xffffffff800040aa <+28>: addi sp,sp,16 0xffffffff800040ac <+30>: ret 0xffffffff800040ae <+32>: lw a5,0(a4) # ticket spinlock start 0xffffffff800040b0 <+34>: sext.w a5,a5 0xffffffff800040b2 <+36>: fence rw,w 0xffffffff800040b6 <+40>: addiw a5,a5,1 0xffffffff800040b8 <+42>: slli a5,a5,0x30 0xffffffff800040ba <+44>: srli a5,a5,0x30 0xffffffff800040bc <+46>: sh a5,0(a4) # ticket spinlock end 0xffffffff800040c0 <+50>: ld s0,8(sp) 0xffffffff800040c2 <+52>: addi sp,sp,16 0xffffffff800040c4 <+54>: ret The qspinlock is smaller and faster than ticket-lock when all are in fast-path, and combo spinlock could provide a compatible Linux Image for different micro-arch design (weak/strict fwd guarantee LR/SC) processors. Signed-off-by:Guo Ren <guoren@kernel.org> Signed-off-by:
Guo Ren <guoren@linux.alibaba.com>
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