From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 6A8D843208 for ; Thu, 26 Oct 2023 15:43:42 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 15C6042E31; Thu, 26 Oct 2023 15:43:42 +0200 (CEST) Received: from out5-smtp.messagingengine.com (out5-smtp.messagingengine.com [66.111.4.29]) by mails.dpdk.org (Postfix) with ESMTP id 1CCB14003C; Thu, 26 Oct 2023 15:43:26 +0200 (CEST) Received: from compute6.internal (compute6.nyi.internal [10.202.2.47]) by mailout.nyi.internal (Postfix) with ESMTP id B79DC5C02A4; Thu, 26 Oct 2023 09:43:25 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute6.internal (MEProxy); Thu, 26 Oct 2023 09:43:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= cc:cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:sender:subject:subject:to:to; s=fm3; t= 1698327805; x=1698414205; bh=7sTmaIT0e7I4nnNIMOGXeeknjvwrXD9eyN4 +iGNbsOQ=; b=KOrUH5EbfnccVzMPnQf+PDaProTwvTIjrciFZYj6VmhAyLPOZSj Ct0OhMa6/4b8JGrdPSfOO53mryzvRYZQJS6GQIDypYXQCGUnqbDxKHi6ZDXXycfz pvLQ/upYEc8LgrCwL6IITVtxozNkz0o9p1N1eE+imo0BmMW0cQL4ecmYp0mMUJj8 rjgPn/e5fikN09w5XE6n3esNihTejhhRLt206e4cL+l0RFXcPHSKOY43P1lit3jx NB6z2kAWJbrMD47seNTLs4FbpZsRWU+oXYAWcvPmUW6NRqnqP/R/jfX7tnMB5Fum npyzDU8MJoFoOPOuzH8C9MOF0lWYeB9fLsQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:sender:subject:subject:to:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t= 1698327805; x=1698414205; bh=7sTmaIT0e7I4nnNIMOGXeeknjvwrXD9eyN4 +iGNbsOQ=; b=TE+PdqYLwFna9CVEQO1eU3XZhvZ7mqmpVLplCmaCXqmw6auEGE8 JPIZiscZ3XmX1HC31SAoX7mIjP9RDyEasz3QpUCQAcPlIQv8CVy2twe24BHVYvuy uASpxC30NvXvFCYFkbOP/Cd6zWXb6VgOEf2qxinPXPdOVaEzxv1PmtSV1WJlE0Wf hm4zKRUAS0+k8MFbEzURCI3GYqx0Xh4eVhIuhQBYvD0ADc30ykdbF912LBVsKj4E 7HLFHxyW6PczGszclC47Zg782EdH5rX1gzwu40hJ/heeCXtpWq7c3FxLgDtO7ka0 uEOgwWcRlfq07eAP4kAuQx2GsI1ICnJwr/A== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvkedrledvgdeikecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpefhvfevufffkffojghfgggtgfesthekredtredtjeenucfhrhhomhepvfhhohhm rghsucfoohhnjhgrlhhonhcuoehthhhomhgrshesmhhonhhjrghlohhnrdhnvghtqeenuc ggtffrrghtthgvrhhnpedtieffffegfeetlefhkeeuteeuudffjefgleevtdeijedukefg veehteehheegjeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfh hrohhmpehthhhomhgrshesmhhonhhjrghlohhnrdhnvght X-ME-Proxy: Feedback-ID: i47234305:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Thu, 26 Oct 2023 09:43:23 -0400 (EDT) From: Thomas Monjalon To: dev@dpdk.org Cc: David Marchand , stable@dpdk.org, =?UTF-8?q?Morten=20Br=C3=B8rup?= , Anatoly Burakov , Stephen Hemminger , Narcisa Vasile , Tyler Retzlaff , Dmitry Kozlyuk , Andrew Rybchenko , Konstantin Ananyev Subject: [PATCH v4 2/2] eal/unix: allow creating thread with real-time priority Date: Thu, 26 Oct 2023 15:37:42 +0200 Message-ID: <20231026134313.1165954-3-thomas@monjalon.net> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231026134313.1165954-1-thomas@monjalon.net> References: <20231024125416.798897-1-thomas@monjalon.net> <20231026134313.1165954-1-thomas@monjalon.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org When adding an API for creating threads, the real-time priority has been forbidden on Unix. There is a known issue with ring behaviour, but it should not be completely forbidden. Real-time thread can block some kernel threads on the same core, making the system unstable. That's why a pause is added in the test thread. Fixes: ca04c78b6262 ("eal: get/set thread priority per thread identifier") Fixes: ce6e911d20f6 ("eal: add thread lifetime API") Fixes: a7ba40b2b1bf ("drivers: convert to internal control threads") Cc: stable@dpdk.org Signed-off-by: Thomas Monjalon Acked-by: Morten Brørup --- app/test/test_threads.c | 11 +--------- .../prog_guide/env_abstraction_layer.rst | 4 +++- lib/eal/include/rte_thread.h | 8 +++++-- lib/eal/unix/rte_thread.c | 21 +++++++++++-------- 4 files changed, 22 insertions(+), 22 deletions(-) diff --git a/app/test/test_threads.c b/app/test/test_threads.c index 4ac3f2671a..c14d39fc83 100644 --- a/app/test/test_threads.c +++ b/app/test/test_threads.c @@ -22,7 +22,7 @@ thread_main(void *arg) __atomic_store_n(&thread_id_ready, 1, __ATOMIC_RELEASE); while (__atomic_load_n(&thread_id_ready, __ATOMIC_ACQUIRE) == 1) - ; + rte_thread_yield_realtime(); /* required for RT priority */ return 0; } @@ -97,21 +97,12 @@ test_thread_priority(void) "Priority set mismatches priority get"); priority = RTE_THREAD_PRIORITY_REALTIME_CRITICAL; -#ifndef RTE_EXEC_ENV_WINDOWS - RTE_TEST_ASSERT(rte_thread_set_priority(thread_id, priority) == ENOTSUP, - "Priority set to critical should fail"); - RTE_TEST_ASSERT(rte_thread_get_priority(thread_id, &priority) == 0, - "Failed to get thread priority"); - RTE_TEST_ASSERT(priority == RTE_THREAD_PRIORITY_NORMAL, - "Failed set to critical should have retained normal"); -#else RTE_TEST_ASSERT(rte_thread_set_priority(thread_id, priority) == 0, "Priority set to critical should succeed"); RTE_TEST_ASSERT(rte_thread_get_priority(thread_id, &priority) == 0, "Failed to get thread priority"); RTE_TEST_ASSERT(priority == RTE_THREAD_PRIORITY_REALTIME_CRITICAL, "Priority set mismatches priority get"); -#endif priority = RTE_THREAD_PRIORITY_NORMAL; RTE_TEST_ASSERT(rte_thread_set_priority(thread_id, priority) == 0, diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst index 6debf54efb..d1f7cae7cd 100644 --- a/doc/guides/prog_guide/env_abstraction_layer.rst +++ b/doc/guides/prog_guide/env_abstraction_layer.rst @@ -815,7 +815,9 @@ Known Issues 4. It MAY be used by preemptible multi-producer and/or preemptible multi-consumer pthreads whose scheduling policy are all SCHED_OTHER(cfs), SCHED_IDLE or SCHED_BATCH. User SHOULD be aware of the performance penalty before using it. - 5. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR. + 5. It MUST not be used by multi-producer/consumer pthreads + whose scheduling policies are ``SCHED_FIFO`` + or ``SCHED_RR`` (``RTE_THREAD_PRIORITY_REALTIME_CRITICAL``). Alternatively, applications can use the lock-free stack mempool handler. When considering this handler, note that: diff --git a/lib/eal/include/rte_thread.h b/lib/eal/include/rte_thread.h index f2581fe152..7ff031e1b2 100644 --- a/lib/eal/include/rte_thread.h +++ b/lib/eal/include/rte_thread.h @@ -56,10 +56,14 @@ typedef uint32_t (*rte_thread_func) (void *arg); * Thread priority values. */ enum rte_thread_priority { + /** Normal thread priority, the default. */ RTE_THREAD_PRIORITY_NORMAL = 0, - /**< normal thread priority, the default */ + /** + * Highest thread priority, use with caution. + * WARNING: System may be unstable because of a real-time busy loop. + * @see rte_thread_yield_realtime(). + */ RTE_THREAD_PRIORITY_REALTIME_CRITICAL = 1, - /**< highest thread priority allowed */ }; /** diff --git a/lib/eal/unix/rte_thread.c b/lib/eal/unix/rte_thread.c index d0758f23bb..e9967e7e41 100644 --- a/lib/eal/unix/rte_thread.c +++ b/lib/eal/unix/rte_thread.c @@ -51,6 +51,18 @@ thread_map_priority_to_os_value(enum rte_thread_priority eal_pri, int *os_pri, sched_get_priority_max(SCHED_OTHER)) / 2; break; case RTE_THREAD_PRIORITY_REALTIME_CRITICAL: + /* + * WARNING: Real-time busy loop takes priority on kernel threads, + * making the system unstable. + * There is also a known issue when using rte_ring. + */ + static bool warned; + if (!warned) { + RTE_LOG(NOTICE, EAL, + "Real-time thread is unstable if polling without sleep.\n"); + warned = true; + } + *pol = SCHED_RR; *os_pri = sched_get_priority_max(SCHED_RR); break; @@ -155,11 +167,6 @@ rte_thread_create(rte_thread_t *thread_id, goto cleanup; } - if (thread_attr->priority == - RTE_THREAD_PRIORITY_REALTIME_CRITICAL) { - ret = ENOTSUP; - goto cleanup; - } ret = thread_map_priority_to_os_value(thread_attr->priority, ¶m.sched_priority, &policy); if (ret != 0) @@ -292,10 +299,6 @@ rte_thread_set_priority(rte_thread_t thread_id, int policy; int ret; - /* Realtime priority can cause crashes on non-Windows platforms. */ - if (priority == RTE_THREAD_PRIORITY_REALTIME_CRITICAL) - return ENOTSUP; - ret = thread_map_priority_to_os_value(priority, ¶m.sched_priority, &policy); if (ret != 0) -- 2.42.0