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GET /api/patches/133432/?format=api
{ "id": 133432, "url": "https://patches.dpdk.org/api/patches/133432/?format=api", "web_url": "https://patches.dpdk.org/project/dpdk/patch/20231026142749.1174372-3-thomas@monjalon.net/", "project": { "id": 1, "url": "https://patches.dpdk.org/api/projects/1/?format=api", "name": "DPDK", "link_name": "dpdk", "list_id": "dev.dpdk.org", "list_email": "dev@dpdk.org", "web_url": "http://core.dpdk.org", "scm_url": "git://dpdk.org/dpdk", "webscm_url": "http://git.dpdk.org/dpdk", "list_archive_url": "https://inbox.dpdk.org/dev", "list_archive_url_format": "https://inbox.dpdk.org/dev/{}", "commit_url_format": "" }, "msgid": "<20231026142749.1174372-3-thomas@monjalon.net>", "list_archive_url": "https://inbox.dpdk.org/dev/20231026142749.1174372-3-thomas@monjalon.net", "date": "2023-10-26T14:19:37", "name": "[v5,2/2] eal/unix: allow creating thread with real-time priority", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": true, "hash": "13d9f0dc7a6c32c7968271ab85fdb56edfd15a9c", "submitter": { "id": 685, "url": "https://patches.dpdk.org/api/people/685/?format=api", "name": "Thomas Monjalon", "email": "thomas@monjalon.net" }, "delegate": { "id": 1, "url": "https://patches.dpdk.org/api/users/1/?format=api", "username": "tmonjalo", "first_name": "Thomas", "last_name": "Monjalon", "email": "thomas@monjalon.net" }, "mbox": "https://patches.dpdk.org/project/dpdk/patch/20231026142749.1174372-3-thomas@monjalon.net/mbox/", "series": [ { "id": 30007, "url": "https://patches.dpdk.org/api/series/30007/?format=api", "web_url": "https://patches.dpdk.org/project/dpdk/list/?series=30007", "date": "2023-10-26T14:19:35", "name": "allow creating thread with real-time priority", "version": 5, "mbox": "https://patches.dpdk.org/series/30007/mbox/" } ], "comments": "https://patches.dpdk.org/api/patches/133432/comments/", "check": "fail", "checks": "https://patches.dpdk.org/api/patches/133432/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<dev-bounces@dpdk.org>", "X-Original-To": "patchwork@inbox.dpdk.org", "Delivered-To": "patchwork@inbox.dpdk.org", "Received": [ "from mails.dpdk.org (mails.dpdk.org [217.70.189.124])\n\tby inbox.dpdk.org (Postfix) with ESMTP id 2C5A743209;\n\tThu, 26 Oct 2023 16:28:08 +0200 (CEST)", "from mails.dpdk.org (localhost [127.0.0.1])\n\tby mails.dpdk.org (Postfix) with ESMTP id F29A842E19;\n\tThu, 26 Oct 2023 16:28:02 +0200 (CEST)", "from out5-smtp.messagingengine.com (out5-smtp.messagingengine.com\n [66.111.4.29]) by mails.dpdk.org (Postfix) with ESMTP id D760342E16;\n Thu, 26 Oct 2023 16:28:00 +0200 (CEST)", "from compute6.internal (compute6.nyi.internal [10.202.2.47])\n by mailout.nyi.internal (Postfix) with ESMTP id 80C765C0180;\n Thu, 26 Oct 2023 10:28:00 -0400 (EDT)", "from mailfrontend2 ([10.202.2.163])\n by compute6.internal (MEProxy); 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charset=UTF-8", "Content-Transfer-Encoding": "8bit", "X-BeenThere": "dev@dpdk.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "DPDK patches and discussions <dev.dpdk.org>", "List-Unsubscribe": "<https://mails.dpdk.org/options/dev>,\n <mailto:dev-request@dpdk.org?subject=unsubscribe>", "List-Archive": "<http://mails.dpdk.org/archives/dev/>", "List-Post": "<mailto:dev@dpdk.org>", "List-Help": "<mailto:dev-request@dpdk.org?subject=help>", "List-Subscribe": "<https://mails.dpdk.org/listinfo/dev>,\n <mailto:dev-request@dpdk.org?subject=subscribe>", "Errors-To": "dev-bounces@dpdk.org" }, "content": "When adding an API for creating threads,\nthe real-time priority has been forbidden on Unix.\n\nThere is a known issue with ring behaviour,\nbut it should not be completely forbidden.\n\nReal-time thread can block some kernel threads on the same core,\nmaking the system unstable.\nThat's why a sleep is added in the test thread,\nand a warning is logged when using real-time priority.\n\nFixes: ca04c78b6262 (\"eal: get/set thread priority per thread identifier\")\nFixes: ce6e911d20f6 (\"eal: add thread lifetime API\")\nFixes: a7ba40b2b1bf (\"drivers: convert to internal control threads\")\nCc: stable@dpdk.org\n\nSigned-off-by: Thomas Monjalon <thomas@monjalon.net>\nAcked-by: Morten Brørup <mb@smartsharesystems.com>\n---\n app/test/test_threads.c | 11 +---------\n .../prog_guide/env_abstraction_layer.rst | 4 +++-\n lib/eal/include/rte_thread.h | 8 +++++--\n lib/eal/unix/rte_thread.c | 22 +++++++++++--------\n 4 files changed, 23 insertions(+), 22 deletions(-)", "diff": "diff --git a/app/test/test_threads.c b/app/test/test_threads.c\nindex 4ac3f2671a..c14d39fc83 100644\n--- a/app/test/test_threads.c\n+++ b/app/test/test_threads.c\n@@ -22,7 +22,7 @@ thread_main(void *arg)\n \t__atomic_store_n(&thread_id_ready, 1, __ATOMIC_RELEASE);\n \n \twhile (__atomic_load_n(&thread_id_ready, __ATOMIC_ACQUIRE) == 1)\n-\t\t;\n+\t\trte_thread_yield_realtime(); /* required for RT priority */\n \n \treturn 0;\n }\n@@ -97,21 +97,12 @@ test_thread_priority(void)\n \t\t\"Priority set mismatches priority get\");\n \n \tpriority = RTE_THREAD_PRIORITY_REALTIME_CRITICAL;\n-#ifndef RTE_EXEC_ENV_WINDOWS\n-\tRTE_TEST_ASSERT(rte_thread_set_priority(thread_id, priority) == ENOTSUP,\n-\t\t\"Priority set to critical should fail\");\n-\tRTE_TEST_ASSERT(rte_thread_get_priority(thread_id, &priority) == 0,\n-\t\t\"Failed to get thread priority\");\n-\tRTE_TEST_ASSERT(priority == RTE_THREAD_PRIORITY_NORMAL,\n-\t\t\"Failed set to critical should have retained normal\");\n-#else\n \tRTE_TEST_ASSERT(rte_thread_set_priority(thread_id, priority) == 0,\n \t\t\"Priority set to critical should succeed\");\n \tRTE_TEST_ASSERT(rte_thread_get_priority(thread_id, &priority) == 0,\n \t\t\"Failed to get thread priority\");\n \tRTE_TEST_ASSERT(priority == RTE_THREAD_PRIORITY_REALTIME_CRITICAL,\n \t\t\"Priority set mismatches priority get\");\n-#endif\n \n \tpriority = RTE_THREAD_PRIORITY_NORMAL;\n \tRTE_TEST_ASSERT(rte_thread_set_priority(thread_id, priority) == 0,\ndiff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst\nindex 6debf54efb..d1f7cae7cd 100644\n--- a/doc/guides/prog_guide/env_abstraction_layer.rst\n+++ b/doc/guides/prog_guide/env_abstraction_layer.rst\n@@ -815,7 +815,9 @@ Known Issues\n \n 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.\n \n- 5. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR.\n+ 5. It MUST not be used by multi-producer/consumer pthreads\n+ whose scheduling policies are ``SCHED_FIFO``\n+ or ``SCHED_RR`` (``RTE_THREAD_PRIORITY_REALTIME_CRITICAL``).\n \n Alternatively, applications can use the lock-free stack mempool handler. When\n considering this handler, note that:\ndiff --git a/lib/eal/include/rte_thread.h b/lib/eal/include/rte_thread.h\nindex f2581fe152..7ff031e1b2 100644\n--- a/lib/eal/include/rte_thread.h\n+++ b/lib/eal/include/rte_thread.h\n@@ -56,10 +56,14 @@ typedef uint32_t (*rte_thread_func) (void *arg);\n * Thread priority values.\n */\n enum rte_thread_priority {\n+\t/** Normal thread priority, the default. */\n \tRTE_THREAD_PRIORITY_NORMAL = 0,\n-\t/**< normal thread priority, the default */\n+\t/**\n+\t * Highest thread priority, use with caution.\n+\t * WARNING: System may be unstable because of a real-time busy loop.\n+\t * @see rte_thread_yield_realtime().\n+\t */\n \tRTE_THREAD_PRIORITY_REALTIME_CRITICAL = 1,\n-\t/**< highest thread priority allowed */\n };\n \n /**\ndiff --git a/lib/eal/unix/rte_thread.c b/lib/eal/unix/rte_thread.c\nindex 278d8d342d..17ffb86c17 100644\n--- a/lib/eal/unix/rte_thread.c\n+++ b/lib/eal/unix/rte_thread.c\n@@ -33,6 +33,8 @@ static int\n thread_map_priority_to_os_value(enum rte_thread_priority eal_pri, int *os_pri,\n \tint *pol)\n {\n+\tstatic bool warned;\n+\n \t/* Clear the output parameters. */\n \t*os_pri = sched_get_priority_min(SCHED_OTHER) - 1;\n \t*pol = -1;\n@@ -51,6 +53,17 @@ thread_map_priority_to_os_value(enum rte_thread_priority eal_pri, int *os_pri,\n \t\t\tsched_get_priority_max(SCHED_OTHER)) / 2;\n \t\tbreak;\n \tcase RTE_THREAD_PRIORITY_REALTIME_CRITICAL:\n+\t\t/*\n+\t\t * WARNING: Real-time busy loop takes priority on kernel threads,\n+\t\t * making the system unstable.\n+\t\t * There is also a known issue when using rte_ring.\n+\t\t */\n+\t\tif (!warned) {\n+\t\t\tRTE_LOG(NOTICE, EAL,\n+\t\t\t\t\t\"Real-time thread is unstable if polling without sleep.\\n\");\n+\t\t\twarned = true;\n+\t\t}\n+\n \t\t*pol = SCHED_RR;\n \t\t*os_pri = sched_get_priority_max(SCHED_RR);\n \t\tbreak;\n@@ -155,11 +168,6 @@ rte_thread_create(rte_thread_t *thread_id,\n \t\t\tgoto cleanup;\n \t\t}\n \n-\t\tif (thread_attr->priority ==\n-\t\t\t\tRTE_THREAD_PRIORITY_REALTIME_CRITICAL) {\n-\t\t\tret = ENOTSUP;\n-\t\t\tgoto cleanup;\n-\t\t}\n \t\tret = thread_map_priority_to_os_value(thread_attr->priority,\n \t\t\t\t¶m.sched_priority, &policy);\n \t\tif (ret != 0)\n@@ -291,10 +299,6 @@ rte_thread_set_priority(rte_thread_t thread_id,\n \tint policy;\n \tint ret;\n \n-\t/* Realtime priority can cause crashes on non-Windows platforms. */\n-\tif (priority == RTE_THREAD_PRIORITY_REALTIME_CRITICAL)\n-\t\treturn ENOTSUP;\n-\n \tret = thread_map_priority_to_os_value(priority, ¶m.sched_priority,\n \t\t&policy);\n \tif (ret != 0)\n", "prefixes": [ "v5", "2/2" ] }