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t=1679617109; bh=baE66WAvlZt1HEma7dXFYnUtrxITRNKnebLiWstMAi0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=KdkjjS5Af4jGRn7QyBMyhVuzQXg8S/DTIrDEHFXwxZJTNxYSdpJ/ct0igEN4HIMYT xrkRTN+FquckOVHs4tLMgaZzhTX1J1xuvQD6psiXCwjpIN4ZTdva64kQB4WD376gSw wh0QVaTIhNWXj3t6kZzb7+sGcOs0Acx7Up3LIf0KaUFsC0/RM3kxQrpGBfqxSOPlTz NaQDXrQxl95qgqzjluwUNC4Ej1Zd5oDB4vdQSEDO3hqW5XPh/clzt6KAihIi8edsTW 97/2cTTcGOXhPytXt4Xh8VOYriWkzP7ANGQzW9YIWM7BN36UL4eWJr8uAiRxSx47D8 g6XZS/qBA1vmg== Date: Fri, 24 Mar 2023 08:18:24 +0800 From: Masami Hiramatsu (Google) To: Beau Belgrave Cc: rostedt@goodmis.org, mathieu.desnoyers@efficios.com, dcook@linux.microsoft.com, alanau@linux.microsoft.com, brauner@kernel.org, akpm@linux-foundation.org, ebiederm@xmission.com, keescook@chromium.org, tglx@linutronix.de, linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka Subject: Re: [PATCH v8 11/11] tracing/user_events: Limit global user_event count Message-Id: <20230324081824.b917c2944da217e5239e1223@kernel.org> In-Reply-To: <20230221211143.574-12-beaub@linux.microsoft.com> References: <20230221211143.574-1-beaub@linux.microsoft.com> <20230221211143.574-12-beaub@linux.microsoft.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8641CC0021 X-Stat-Signature: negnpsuhj75oa9u5yqssgeggyjrhqf3w X-HE-Tag: 1679617111-482034 X-HE-Meta: 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 rEx2mCoV 1f3r1Q7a1J0eeKnhWCTMRp8c9cAj1XdWMa4K284dP1ptMpfzXXQ4qXdXxmb4qLGHYRuJO71lZ6Nf4dzHhlr3j7olNf81chUIih7XiiJdsAx8IotLw0KIRQFChCMK1xjA4oi3OaPvIrXM2LrJzJcYS2Kb4PBwNgB+PC4C7F77v0fWRaAXMR+LrpjE8ngayUkfW8705NOJBrjxKJ50DPFqN8weTdjA/p4x+JqWNJd16JHR61na2O6CErlNlsgQjMIMb1lHDnu2AepCuJw1X7NTO1ptywbeX/RZbjo4oV65ZmAI+8+DLg3N8eH7lNzvS+jhB4RzWTYAicE53N4+XgGgHqserUCFABhqVsiHgNnDGrHj/VSiPwR/NQ5Al5x5H/SjOzHlyIVzmgkBgSY+Eb91ibDLrBfprGEUenaJPycPr4j2jXkDembQ3B/u0hN2MZF6PLUfrBfdIZmN7lqklz1X3K3dk+g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Beau, On Tue, 21 Feb 2023 13:11:43 -0800 Beau Belgrave wrote: > Operators want to be able to ensure enough tracepoints exist on the > system for kernel components as well as for user components. Since there > are only up to 64K events, by default allow up to half to be used by > user events. > > Add a boot parameter (user_events_max=%d) and a kernel sysctl parameter > (kernel.user_events_max) to set a global limit that is honored among all > groups on the system. This ensures hard limits can be setup to prevent > user processes from consuming all event IDs on the system. sysctl is good to me, but would we really need the kernel parameter? The user_events starts using when user-space is up, so I think setting the limit with sysctl is enough. BTW, Vlastimil tried to add 'sysctl.*' kernel parameter support(*). If we need a kernel cmdline support, I think this is more generic way. But it seems the discussion has been stopped. (*) https://patchwork.kernel.org/project/linux-mm/patch/20200427180433.7029-2-vbabka@suse.cz/ Thank you, > > Signed-off-by: Beau Belgrave > --- > kernel/trace/trace_events_user.c | 59 ++++++++++++++++++++++++++++++++ > 1 file changed, 59 insertions(+) > > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c > index 222f2eb59c7c..6a5ebe243999 100644 > --- a/kernel/trace/trace_events_user.c > +++ b/kernel/trace/trace_events_user.c > @@ -20,6 +20,7 @@ > #include > #include > #include > +#include > #include > #include "trace.h" > #include "trace_dynevent.h" > @@ -61,6 +62,12 @@ struct user_event_group { > /* Group for init_user_ns mapping, top-most group */ > static struct user_event_group *init_group; > > +/* Max allowed events for the whole system */ > +static unsigned int max_user_events = 32768; > + > +/* Current number of events on the whole system */ > +static unsigned int current_user_events; > + > /* > * Stores per-event properties, as users register events > * within a file a user_event might be created if it does not > @@ -1241,6 +1248,8 @@ static int destroy_user_event(struct user_event *user) > { > int ret = 0; > > + lockdep_assert_held(&event_mutex); > + > /* Must destroy fields before call removal */ > user_event_destroy_fields(user); > > @@ -1257,6 +1266,11 @@ static int destroy_user_event(struct user_event *user) > kfree(EVENT_NAME(user)); > kfree(user); > > + if (current_user_events > 0) > + current_user_events--; > + else > + pr_alert("BUG: Bad current_user_events\n"); > + > return ret; > } > > @@ -1744,6 +1758,11 @@ static int user_event_parse(struct user_event_group *group, char *name, > > mutex_lock(&event_mutex); > > + if (current_user_events >= max_user_events) { > + ret = -EMFILE; > + goto put_user_lock; > + } > + > ret = user_event_trace_register(user); > > if (ret) > @@ -1755,6 +1774,7 @@ static int user_event_parse(struct user_event_group *group, char *name, > dyn_event_init(&user->devent, &user_event_dops); > dyn_event_add(&user->devent, &user->call); > hash_add(group->register_table, &user->node, key); > + current_user_events++; > > mutex_unlock(&event_mutex); > > @@ -2386,6 +2406,43 @@ static int create_user_tracefs(void) > return -ENODEV; > } > > +static int __init set_max_user_events(char *str) > +{ > + if (!str) > + return 0; > + > + if (kstrtouint(str, 0, &max_user_events)) > + return 0; > + > + return 1; > +} > +__setup("user_events_max=", set_max_user_events); > + > +static int set_max_user_events_sysctl(struct ctl_table *table, int write, > + void *buffer, size_t *lenp, loff_t *ppos) > +{ > + int ret; > + > + mutex_lock(&event_mutex); > + > + ret = proc_douintvec(table, write, buffer, lenp, ppos); > + > + mutex_unlock(&event_mutex); > + > + return ret; > +} > + > +static struct ctl_table user_event_sysctls[] = { > + { > + .procname = "user_events_max", > + .data = &max_user_events, > + .maxlen = sizeof(unsigned int), > + .mode = 0644, > + .proc_handler = set_max_user_events_sysctl, > + }, > + {} > +}; > + > static int __init trace_events_user_init(void) > { > int ret; > @@ -2415,6 +2472,8 @@ static int __init trace_events_user_init(void) > if (dyn_event_register(&user_event_dops)) > pr_warn("user_events could not register with dyn_events\n"); > > + register_sysctl_init("kernel", user_event_sysctls); > + > return 0; > } > > -- > 2.25.1 > -- Masami Hiramatsu (Google)