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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-378956d3840sm16711981f8f.89.2024.09.13.04.34.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Sep 2024 04:34:22 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 13 Sep 2024 13:34:20 +0200 To: Oleg Nesterov Cc: Jiri Olsa , Peter Zijlstra , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Hao Luo , Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCHv3 1/7] uprobe: Add support for session consumer Message-ID: References: <20240909074554.2339984-1-jolsa@kernel.org> <20240909074554.2339984-2-jolsa@kernel.org> <20240912162028.GD27648@redhat.com> <20240913105750.GC19305@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240913105750.GC19305@redhat.com> On Fri, Sep 13, 2024 at 12:57:51PM +0200, Oleg Nesterov wrote: > On 09/13, Jiri Olsa wrote: > > > > I'm not sure the realloc will help, I feel like we need to allocate return > > consumer for each called handler separately to be safe > > How about something like the (pseudo) code below? Note that this way > we do not need uprobe->consumers_cnt. Note also that krealloc() should > be unlikely and it checks ksize() before it does another allocation. > > Oleg. > > static size_t ri_size(int consumers_cnt) > { > return sizeof(struct return_instance) + > sizeof(struct return_consumer) * consumers_cnt; > } > > #define DEF_CNT 4 // arbitrary value > > static struct return_instance *alloc_return_instance(void) > { > struct return_instance *ri; > > ri = kzalloc(ri_size(DEF_CNT), GFP_KERNEL); > if (!ri) > return ZERO_SIZE_PTR; > > ri->consumers_cnt = DEF_CNT; > return ri; > } > > static struct return_instance *push_id_cookie(struct return_instance *ri, int idx, > __u64 id, __u64 cookie) > { > if (unlikely(ri == ZERO_SIZE_PTR)) > return ri; > > if (unlikely(idx >= ri->consumers_cnt)) { > ri->consumers_cnt += DEF_CNT; > ri = krealloc(ri, ri_size(ri->consumers_cnt), GFP_KERNEL); > if (!ri) { > kfree(ri); > return ZERO_SIZE_PTR; > } > } > > ri->consumers[idx].id = id; > ri->consumers[idx].cookie = cookie; > return ri; > } > > static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) > { > ... > struct return_instance *ri = NULL; > int push_idx = 0; > > list_for_each_entry_rcu(uc, &uprobe->consumers, cons_node, rcu_read_lock_trace_held()) { > __u64 cookie = 0; > int rc = 0; > > if (uc->handler) > rc = uc->handler(uc, regs, &cookie); > > remove &= rc; > has_consumers = true; > > if (!uc->ret_handler || rc == UPROBE_HANDLER_REMOVE || rc == 2) > continue; > > if (!ri) > ri = alloc_return_instance(); > > // or, better if (rc = UPROBE_HANDLER_I_WANT_MY_COOKIE) > if (uc->handler)) > ri = push_id_cookie(ri, push_idx++, uc->id, cookie); > } > > if (!ZERO_OR_NULL_PTR(ri)) { should we rather bail out right after we fail to allocate ri above? > ri->consumers_cnt = push_idx; > prepare_uretprobe(uprobe, regs, ri); > } > > ... > } > nice, I like that, will try to to plug it with the rest thanks, jirka