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GET /api/patches/133313/?format=api
HTTP 200 OK
Allow: GET, PUT, PATCH, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "id": 133313,
    "url": "http://patches.dpdk.org/api/patches/133313/?format=api",
    "web_url": "http://patches.dpdk.org/project/dpdk/patch/20231025163352.1076755-3-thomas@monjalon.net/",
    "project": {
        "id": 1,
        "url": "http://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": "<20231025163352.1076755-3-thomas@monjalon.net>",
    "list_archive_url": "https://inbox.dpdk.org/dev/20231025163352.1076755-3-thomas@monjalon.net",
    "date": "2023-10-25T16:31:11",
    "name": "[v3,2/2] eal/unix: allow creating thread with real-time priority",
    "commit_ref": null,
    "pull_url": null,
    "state": "superseded",
    "archived": true,
    "hash": "f47dfb504b8a4c5bbb6d319548ba8a6e17b6a8a6",
    "submitter": {
        "id": 685,
        "url": "http://patches.dpdk.org/api/people/685/?format=api",
        "name": "Thomas Monjalon",
        "email": "thomas@monjalon.net"
    },
    "delegate": {
        "id": 1,
        "url": "http://patches.dpdk.org/api/users/1/?format=api",
        "username": "tmonjalo",
        "first_name": "Thomas",
        "last_name": "Monjalon",
        "email": "thomas@monjalon.net"
    },
    "mbox": "http://patches.dpdk.org/project/dpdk/patch/20231025163352.1076755-3-thomas@monjalon.net/mbox/",
    "series": [
        {
            "id": 29984,
            "url": "http://patches.dpdk.org/api/series/29984/?format=api",
            "web_url": "http://patches.dpdk.org/project/dpdk/list/?series=29984",
            "date": "2023-10-25T16:31:09",
            "name": "allow creating thread with real-time priority",
            "version": 3,
            "mbox": "http://patches.dpdk.org/series/29984/mbox/"
        }
    ],
    "comments": "http://patches.dpdk.org/api/patches/133313/comments/",
    "check": "fail",
    "checks": "http://patches.dpdk.org/api/patches/133313/checks/",
    "tags": {},
    "related": [],
    "headers": {
        "Return-Path": "<dev-bounces@dpdk.org>",
        "X-Original-To": "patchwork@inbox.dpdk.org",
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        ],
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        "Feedback-ID": "i47234305:Fastmail",
        "From": "Thomas Monjalon <thomas@monjalon.net>",
        "To": "dev@dpdk.org",
        "Cc": "David Marchand <david.marchand@redhat.com>, stable@dpdk.org, =?utf-8?q?M?=\n\t=?utf-8?q?orten_Br=C3=B8rup?= <mb@smartsharesystems.com>,\n Anatoly Burakov <anatoly.burakov@intel.com>,\n Stephen Hemminger <stephen@networkplumber.org>,\n Tyler Retzlaff <roretzla@linux.microsoft.com>,\n Narcisa Vasile <navasile@linux.microsoft.com>,\n Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>,\n Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,\n Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>",
        "Subject": "[PATCH v3 2/2] eal/unix: allow creating thread with real-time\n priority",
        "Date": "Wed, 25 Oct 2023 18:31:11 +0200",
        "Message-ID": "<20231025163352.1076755-3-thomas@monjalon.net>",
        "X-Mailer": "git-send-email 2.42.0",
        "In-Reply-To": "<20231025163352.1076755-1-thomas@monjalon.net>",
        "References": "<20231024125416.798897-1-thomas@monjalon.net>\n <20231025163352.1076755-1-thomas@monjalon.net>",
        "MIME-Version": "1.0",
        "Content-Type": "text/plain; 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 pause is added in the test thread.\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 doc/guides/prog_guide/env_abstraction_layer.rst |  4 +++-\n lib/eal/include/rte_thread.h                    |  7 +++++--\n lib/eal/unix/rte_thread.c                       | 14 +++++---------\n 4 files changed, 14 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 139cafac96..1952a10155 100644\n--- a/lib/eal/include/rte_thread.h\n+++ b/lib/eal/include/rte_thread.h\n@@ -56,10 +56,13 @@ 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 */\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 92b4e53adb..87ddf25f1c 100644\n--- a/lib/eal/unix/rte_thread.c\n+++ b/lib/eal/unix/rte_thread.c\n@@ -51,6 +51,11 @@ 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\t*pol = SCHED_RR;\n \t\t*os_pri = sched_get_priority_max(SCHED_RR);\n \t\tbreak;\n@@ -155,11 +160,6 @@ 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&param.sched_priority, &policy);\n \t\tif (ret != 0)\n@@ -291,10 +291,6 @@ 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, &param.sched_priority,\n \t\t&policy);\n \tif (ret != 0)\n",
    "prefixes": [
        "v3",
        "2/2"
    ]
}