linux-kernel - Re: [RFC 08/20] mm: store completed TLB generation

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Message-ID: <YBfrZ+gBCTYFS995@hirez.programming.kicks-ass.net>
Date:   Mon, 1 Feb 2021 12:52:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nadav Amit <nadav.amit@...il.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Nadav Amit <namit@...are.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Nick Piggin <npiggin@...il.com>, x86@...nel.org
Subject: Re: [RFC 08/20] mm: store completed TLB generation

On Sat, Jan 30, 2021 at 04:11:20PM -0800, Nadav Amit wrote:
> +static inline void tlb_update_generation(atomic64_t *gen, u64 new_gen)
> +{
> +	u64 cur_gen = atomic64_read(gen);
> +
> +	while (cur_gen < new_gen) {
> +		u64 old_gen = atomic64_cmpxchg(gen, cur_gen, new_gen);
> +
> +		/* Check if we succeeded in the cmpxchg */
> +		if (likely(cur_gen == old_gen))
> +			break;
> +
> +		cur_gen = old_gen;
> +	};
> +}

	u64 cur_gen = atomic64_read(gen);
	while (cur_gen < new_gen && !atomic64_try_cmpxchg(gen, &cur_gen, new_gen))
		;