From: Richard Henderson <richard.henderson@linaro.org>
To: Michael Clark <mjc@sifive.com>, qemu-devel@nongnu.org
Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>,
Bastian Koppelmann <kbastian@mail.uni-paderborn.de>,
Palmer Dabbelt <palmer@sifive.com>,
Alistair Francis <Alistair.Francis@wdc.com>,
patches@groups.riscv.org
Subject: Re: [Qemu-devel] [PATCH v8 22/35] RISC-V: Use atomic_cmpxchg to update PLIC bitmaps
Date: Thu, 26 Apr 2018 14:14:37 -1000 [thread overview]
Message-ID: <7ec6ba72-fee7-52db-a73a-be1720a06383@linaro.org> (raw)
In-Reply-To: <1524699938-6764-23-git-send-email-mjc@sifive.com>
On 04/25/2018 01:45 PM, Michael Clark wrote:
> + uint32_t old, new;
> + do {
> + old = atomic_read(&plic->pending[word]);
> + new = (old & ~(1 << (irq & 31))) | (-!!pending & (1 << (irq & 31)));
> + } while (atomic_cmpxchg(&plic->pending[word], old, new) != old);
I prefer
uint32_t old, new, cmp = atomic_read(...);
do {
old = cmp;
new = ...;
cmp = atomic_cmpxchg(...);
} while (old != cmp);
to avoid an extra load, should we loop.
That said, what you have is not wrong. So,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
next prev parent reply other threads:[~2018-04-27 0:14 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-25 23:45 [Qemu-devel] [PATCH v8 00/35] QEMU 2.13 Privileged ISA emulation updates Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 01/35] RISC-V: Replace hardcoded constants with enum values Michael Clark
2018-04-26 16:37 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 02/35] RISC-V: Make virt board description match spike Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 03/35] RISC-V: Use ROM base address and size from memmap Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 04/35] RISC-V: Remove identity_translate from load_elf Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 05/35] RISC-V: Remove unused class definitions Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 06/35] RISC-V: Include instruction hex in disassembly Michael Clark
2018-04-26 17:05 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 07/35] RISC-V: Make some header guards more specific Michael Clark
2018-04-26 16:43 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 08/35] RISC-V: Make virt header comment title consistent Michael Clark
2018-04-26 16:42 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 09/35] RISC-V: Remove EM_RISCV ELF_MACHINE indirection Michael Clark
2018-04-26 16:42 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 10/35] RISC-V: Remove erroneous comment from translate.c Michael Clark
2018-04-25 23:51 ` [Qemu-devel] [patches] " Palmer Dabbelt
2018-04-26 16:48 ` [Qemu-devel] " Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 11/35] RISC-V: Mark ROM read-only after copying in code Michael Clark
2018-04-26 16:48 ` Alistair Francis
2018-04-27 5:22 ` Michael Clark
2018-04-27 5:34 ` Michael Clark
2018-04-27 16:17 ` Alistair Francis
2018-05-04 1:45 ` Michael Clark
2018-05-04 23:44 ` Alistair Francis
2018-05-04 23:54 ` Alistair Francis
2018-05-05 2:02 ` Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 12/35] RISC-V: Update address bits to support sv39 and sv48 Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 13/35] RISC-V: Improve page table walker spec compliance Michael Clark
2018-05-03 20:49 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 14/35] RISC-V: Update E order and I extension order Michael Clark
2018-04-26 17:11 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 15/35] RISC-V: Hardwire satp to 0 for no-mmu case Michael Clark
2018-04-26 17:21 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 16/35] RISC-V: Make mtvec/stvec ignore vectored traps Michael Clark
2018-04-26 17:27 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 17/35] RISC-V: No traps on writes to misa, minstret, mcycle Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 18/35] RISC-V: Clear mtval/stval on exceptions without info Michael Clark
2018-04-26 17:36 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 19/35] RISC-V: Allow S-mode mxr access when priv ISA >= v1.10 Michael Clark
2018-04-26 20:02 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 20/35] RISC-V: Use [ms]counteren CSRs " Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 21/35] RISC-V: Add mcycle/minstret support for -icount auto Michael Clark
2018-04-26 20:05 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 22/35] RISC-V: Use atomic_cmpxchg to update PLIC bitmaps Michael Clark
2018-04-27 0:14 ` Richard Henderson [this message]
2018-04-27 7:18 ` Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 23/35] RISC-V: Simplify riscv_cpu_local_irqs_pending Michael Clark
2018-04-27 22:33 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 24/35] RISC-V: Allow setting and clearing multiple irqs Michael Clark
2018-05-03 20:54 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 25/35] RISC-V: Move non-ops from op_helper to cpu_helper Michael Clark
2018-04-26 17:42 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 26/35] RISC-V: Update CSR and interrupt definitions Michael Clark
2018-05-03 20:56 ` Alistair Francis
2018-05-04 4:21 ` Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 27/35] RISC-V: Implement modular CSR helper interface Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 28/35] RISC-V: Implement atomic mip/sip CSR updates Michael Clark
2018-05-03 21:11 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 29/35] RISC-V: Implement existential predicates for CSRs Michael Clark
2018-05-03 21:21 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 30/35] RISC-V: Split out mstatus_fs from tb_flags Michael Clark
2018-05-03 21:22 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 31/35] RISC-V: Mark mstatus.fs dirty Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 32/35] RISC-V: Implement mstatus.TSR/TW/TVM Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 33/35] RISC-V: Add public API for the CSR dispatch table Michael Clark
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 34/35] RISC-V: Add hartid and \n to interrupt logging Michael Clark
2018-05-03 21:25 ` Alistair Francis
2018-04-25 23:45 ` [Qemu-devel] [PATCH v8 35/35] RISC-V: Use riscv prefix consistently on cpu helpers Michael Clark
2018-04-26 1:42 ` [Qemu-devel] [PATCH v8 00/35] QEMU 2.13 Privileged ISA emulation updates Michael Clark
2018-04-26 2:01 ` Michael Clark
2018-04-26 18:22 ` Alistair Francis
2018-04-27 0:34 ` Michael Clark
2018-04-27 10:19 ` Peter Maydell
2018-04-27 0:35 ` Richard Henderson
2018-04-27 5:00 ` Michael Clark
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