From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A777A1D416C; Tue, 29 Sep 2026 23:46:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790725584; cv=none; b=e/9v84vGCp3oud/T53Gqd9AnjP8uSKi1HR9uInNot1WxyGbMo6oLEgGrOdHcRuKVCiD4OQtBOo+hL3luiMGKwxlkUOaj6objG0RnsdJxD/9p3fEytUCiI0DImRaHPV0zFyTVRwoIf1KbzNed4PgJlHUimxp0qyVOzwSf3XNlBJA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790725584; c=relaxed/simple; bh=LRq4vU2UaNtO/ieQAH8HDx9+750FfkGFV8Zr+vB8jWw=; h=Content-Type:MIME-Version:Message-Id:In-Reply-To:References: Subject:From:To:Cc:Date; b=X+4N43FUROXPisi8e4+5L9Xfaxkcq+OnfoHpQS2/07JsgyP11ZSfSyDr0IwGrExQnic90x44o3AiBX0TzZdeHuaeTL65CWnfdNmV76bV9DSIt8CPn/DpgOpaYFSTlNZSxkxMmCXEQ9BbOGoxdcuUv8JL0dpRorhS73j9Qh4/e+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=etKZjUUL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="etKZjUUL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 783C01F000FF; Tue, 29 Sep 2026 23:46:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790725582; bh=eUgBSVCxg479HmVb1My7cssnKyEELh39OZi+wobzssQ=; h=In-Reply-To:References:Subject:From:To:Cc:Date; b=etKZjUULIUryUFPFnSFpQgqe7lgC025pLBPcfJBgF7EIj6RaQUqZQ9lhv5XN8CyaA +yX9+Emy+4optmeHZfwi3fDFg1Aa7/+1YBXdwQ2Ckg948/SfDYt2Awk/2GMKWHoiYh /LtK9tB+/lO6D/tmanLNFiHlETt9k7+MYxFBAZFt/4aFeAcFUDnwhDcEUe6KV8stEN JJmS8poo2aZDL13MgKszUJdqFmnsOWFoD8teIhI0mr2KHBTJDtraL8SUnDeFRt0By7 O4jmVK4ksdsABn2xdPjH1ny3i0pgiS5DQagH3NU2493hELsyE8ZJU0D1eXGYSXNsd6 T3NVyX0leAAnw== Content-Type: multipart/mixed; boundary="===============5723665362160622272==" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <2dc04cf6f1e0c474da152cb4afcd0e264930b4d1d9b969de1b7cfbdd50b1bd35@mail.kernel.org> In-Reply-To: <20260929005411.4105448-2-vineet.gupta@linux.dev> References: <20260929005411.4105448-2-vineet.gupta@linux.dev> Subject: Re: [PATCH v2 1/1] tracing: fgraph: allocate shadow stacks inline with GFP_NOWAIT From: bot+bpf-ci@kernel.org To: vineet.gupta@linux.dev,rostedt@goodmis.org,mhiramat@kernel.org Cc: mark.rutland@arm.com,mathieu.desnoyers@efficios.com,andrii@kernel.org,peterz@infradead.org,linux-trace-kernel@vger.kernel.org,linux-kernel@vger.kernel.org,bpf@vger.kernel.org,kernel-team@meta.com,vineet.gupta@linux.dev,stable@vger.kernel.org,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,mason@kernel.org,ihor.solodrai@linux.dev Date: Tue, 29 Sep 2026 23:46:21 +0000 (UTC) --===============5723665362160622272== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > index ed455b53513b..336f40dc6618 100644 > --- a/kernel/trace/fgraph.c > +++ b/kernel/trace/fgraph.c > @@ -1036,10 +1036,9 @@ trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; > /* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */ > static int alloc_retstack_tasklist(unsigned long **ret_stack_list) > { Does this comment still match the function's behavior? Before the patch, alloc_retstack_tasklist() assigned at most FTRACE_RETSTACK_ALLOC_SIZE stacks per call and returned -EAGAIN to trigger another batch. After the patch, it walks every thread in one pass, allocating inline with GFP_NOWAIT. The FTRACE_RETSTACK_ALLOC_SIZE pre-allocated entries are now only a fallback when GFP_NOWAIT fails, and in the normal case they're all freed at the free: label. > - int i; > - int ret = 0; > int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE; > struct task_struct *g, *t; > + int i, ret = 0; > > if (WARN_ON_ONCE(!fgraph_stack_cachep)) > return -ENOMEM; > @@ -1054,26 +1053,37 @@ static int alloc_retstack_tasklist(unsigned long **ret_stack_list) > } > } > > - rcu_read_lock(); > - for_each_process_thread(g, t) { > - if (start == end) { > - ret = -EAGAIN; > - goto unlock; > - } > + scoped_guard (rcu) { > + for_each_process_thread(g, t) { > + unsigned long *rs; > + > + if (t->ret_stack) > + continue; > + > + rs = kmem_cache_alloc(fgraph_stack_cachep, GFP_NOWAIT); > + if (!rs) { > + /* > + * Returning from inside scoped_guard() drops > + * the RCU read lock, but skips the free loop > + * below. That is only safe because start == > + * end here, which leaves that loop nothing to > + * free. Keep the two in step if this > + * exhaustion check ever changes. > + */ > + if (start == end) > + return -EAGAIN; > + rs = ret_stack_list[start++]; > + } > > - if (t->ret_stack == NULL) { > atomic_set(&t->trace_overrun, 0); > - ret_stack_init_task_vars(ret_stack_list[start]); > + ret_stack_init_task_vars(rs); > t->curr_ret_stack = 0; > t->curr_ret_depth = -1; > /* Make sure the tasks see the 0 first: */ > - smp_wmb(); > - t->ret_stack = ret_stack_list[start++]; > + smp_store_release(&t->ret_stack, rs); > } > } > > -unlock: > - rcu_read_unlock(); > free: > for (i = start; i < end; i++) > kmem_cache_free(fgraph_stack_cachep, ret_stack_list[i]); --- AI reviewed your patch. Please fix the bug or email reply why it's not a bug. See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md CI run summary: https://github.com/kernel-patches/bpf/actions/runs/36644771324 --===============5723665362160622272==--