From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 63E98D3CA for ; Fri, 18 Aug 2023 11:58:11 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 3B63937E2E for ; Fri, 18 Aug 2023 11:57:41 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS for ; Fri, 18 Aug 2023 11:57:38 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id F009642784 for ; Fri, 18 Aug 2023 11:57:37 +0200 (CEST) Message-ID: <4a4edb63-d67b-dc83-216b-719199d4582f@proxmox.com> Date: Fri, 18 Aug 2023 11:57:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 From: Max Carrara To: Wolfgang Bumiller Cc: pbs-devel@lists.proxmox.com References: <20230817164637.1286178-1-m.carrara@proxmox.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SPAM-LEVEL: Spam detection results: 0 AWL 1.996 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment NICE_REPLY_A -4.01 Looks like a legit reply (A) SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: Re: [pbs-devel] [PATCH proxmox] async: runtime: fix `block_in_place` panicking in wrong runtime X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Aug 2023 09:58:11 -0000 On 8/18/23 09:26, Wolfgang Bumiller wrote: > Does a single threaded runtime support `.spawn_blocking()`? Maybe it > would make sense to use that in this case? > It does, yes! However, we can't actually use `spawn_blocking()` inside our `block_in_place()` wrapper; the former is async, the latter is sync. So, I'll think of some other alternatives. Maybe some additional helpers would work instead? Something like: fn try_block_in_place(func: F) -> Result where F: FnOnce() -> R { ... } Basically returning the original closure if `tokio::task::block_in_place()` cannot be called. > Because this just seems a tiny bit dangerous. > Then again, `block_in_place` is the wrong helper if the blocking > operation also depends on any futures making progress, it should only be > used for independent operations... but that doesn't mean it can't > accidentally happen somehow... I'm not sure there's any way to prevent this from happening accidentally. Maybe we can document this to make it apparent when `block_in_place()` is appropriate and when it isn't? I'd include that in the v2 in that case. FWIW, there's a way[0] to re-enter an async context while within `block_in_place()` using `Handle::block_on()`[1]: use tokio::task; use tokio::runtime::Handle; task::block_in_place(move || { Handle::current().block_on(async move { // do something async }); }); This isn't really ideal either imo (because why block when you depend on other futures? There are better ways to do that) but I guess it's useful to know. [0]: https://docs.rs/tokio/latest/tokio/task/fn.block_in_place.html#examples [1]: https://docs.rs/tokio/latest/tokio/runtime/struct.Handle.html#method.block_on > Ideally we could get rid of all the block-in-place stuff without slowing > things down too much, but the latter part is difficult :-) > > On Thu, Aug 17, 2023 at 06:46:37PM +0200, Max Carrara wrote: >> Because `tokio::task::block_in_place` panics if called in the >> "current_thread" runtime, so does our wrapper function. >> >> This is fixed by checking whether we're actually in a multithreaded >> tokio runtime. >> >> Signed-off-by: Max Carrara >> --- >> proxmox-async/src/runtime.rs | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/proxmox-async/src/runtime.rs b/proxmox-async/src/runtime.rs >> index 0fe9fae..35cf7c3 100644 >> --- a/proxmox-async/src/runtime.rs >> +++ b/proxmox-async/src/runtime.rs >> @@ -15,7 +15,12 @@ thread_local! { >> } >> >> fn is_in_tokio() -> bool { >> - tokio::runtime::Handle::try_current().is_ok() >> + tokio::runtime::Handle::try_current().is_ok_and(|rt_handle| { >> + matches!( >> + rt_handle.runtime_flavor(), >> + tokio::runtime::RuntimeFlavor::MultiThread >> + ) >> + }) >> } >> >> fn is_blocking() -> bool { >> -- >> 2.39.2