From nobody Fri Aug 26 16:35:09 2022 X-Original-To: bugs@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4MDlmv1RNZz4ZS2Z for ; Fri, 26 Aug 2022 16:35:11 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4MDlmv0NvMz3Kk7 for ; Fri, 26 Aug 2022 16:35:11 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4MDlmt6YcvzSXS for ; Fri, 26 Aug 2022 16:35:10 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id 27QGZAia011500 for ; Fri, 26 Aug 2022 16:35:10 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 27QGZAkI011499 for bugs@FreeBSD.org; Fri, 26 Aug 2022 16:35:10 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 265974] SMR has several missing barriers Date: Fri, 26 Aug 2022 16:35:09 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: markj@FreeBSD.org X-Bugzilla-Status: Open X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_status Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: Bug reports List-Archive: https://lists.freebsd.org/archives/freebsd-bugs List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-bugs@freebsd.org MIME-Version: 1.0 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1661531711; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Y963JWPCMRYMauv4cTkr3FbuuIXKZVvjo4HZTqNwS+s=; b=EDCFdSQ9c6TuOu1SJRG0NVLeixv1CpJ/LxB9YxL5WRY6tLz7exB7Y1itYR4XGpkd+DwPso NbhlILDWXHd+DYKbv6yg6+hAx7h8dFv8JYzt7qxTFHyHPBeiB4ZJ5yNjVmeWEcGxOA+BQS aeAkSouDQPpEKVFD2rXnLZWL6yMqy6fO5owhlTmZVcfC26EBVCSWKrA9xYgRfbRtMSjbcT HUsjE5FZX9vDQFHLO00g9X9TPQ6zXNRG0hlx79GZCqJkZiVsZBOXbnyTYB0F3DaE7vzvgD AAgpPpa7HkwVaZGqmwnOnOwf3/xl0A7wqDvGMRxjzBwrQP97pddkofUrMyhGZw== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1661531711; a=rsa-sha256; cv=none; b=DqoVqa70PZb9MkEQO7O4PWrWErCnq+6wegzfBa9LM84LmatJn3DGMgnCnEqhuJIzrMvZrS 5Ki1nGBAm3K374RsYtPHFR84IZ8TbTZZVS24Kv0h65caJwZ0sAxGcWVSijAq2uVwFoYBbe XFdsrP9LGezKw6gdTdOjH6KVGnz4JcIGzVVeV10VNSw0hmZ+t3ZCdJZij2jBTcH8y8ghS6 gHBPvx8FTofzAd10bKpOgnopJaITYk1cVHje66Yt5Vu3d7WPpZgctrfAC7g/RWL1YTYg78 RKKIlaGc+pgacZQhZ0jWdEq6CympildWEJWVCQN76wnv8U6wvfT65AkSbmM0Dw== ARC-Authentication-Results: i=1; mx1.freebsd.org; none X-ThisMailContainsUnwantedMimeParts: N https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D265974 Mark Johnston changed: What |Removed |Added ---------------------------------------------------------------------------- Status|New |Open --- Comment #4 from Mark Johnston --- I certainly agree with the comment about smr_enter(). On at least arm64, atomic_add_acq_int()'s acquire semantics apply only to the load; subsequent loads can be reordered with the store. I believe this is true with LSE ato= mics as well as the original LL/SC atomics. I also agree that the code is fine = on Intel since atomic instructions prevent store-load reordering. Our atomic(9) documentation doesn't really call out this subtlety. We might have similar bugs elsewhere. I need to think about smr_poll() a bit more. > Moreover, smr_poll() absolutely needs a full memory barrier on entry, the= `atomic_load_acq_int` performed by `smr_poll` aren't sufficient. The suggested patch adds two barriers to smr_poll_scan() and none to smr_poll(), is that intentional? --=20 You are receiving this mail because: You are the assignee for the bug.=