From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) (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 C187A34EF1B; Tue, 27 Jan 2026 15:22:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769527362; cv=none; b=dxtDZYOmM9BXQAxPGpG8L9UG+clD6C1xWRjVlQyxHIjnDx0WoyP1T3Vwu3RCzEDo2HDOKviRscv8mGqqBTaBrjOHuSh8yk/kGjXEdekys/FCzdgsDuDuYrHk7h+O8eSxhy/a8mMVrF0a/Y7InkwhUqW+DkZrLDPCjpZTbp5Pbig= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769527362; c=relaxed/simple; bh=Hou3k/YcDUMSmtvqCulcR2nRe7AtIjNjZF4uNZFK+O0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=g4b0bBN60YmeKbd78SLq5OGqFSMR+k+OmvxNK7Q6GwdEwpPRVSMH4+IcnPQBazfyKi4LcW9sJBGns0XYWqEnOpT4YUaytZgtuNlQ3YjyBAIfj5CgkbqNs6BkYlkyIAcOhQh35/O1b9wODfjj1pDKpEPpO94B9P1LL23WD0WxNdk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id D832814012A; Tue, 27 Jan 2026 15:22:32 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf14.hostedemail.com (Postfix) with ESMTPA id 56F3D2D; Tue, 27 Jan 2026 15:22:29 +0000 (UTC) Date: Tue, 27 Jan 2026 10:22:34 -0500 From: Steven Rostedt To: Guenter Roeck Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Thomas Gleixner Subject: Re: [RESEND][PATCH 3/5] perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULL Message-ID: <20260127102234.755d8c4e@gandalf.local.home> In-Reply-To: <27f9a957-67c7-4c88-b320-0f8725e9b03d@roeck-us.net> References: <20250820180338.701352023@kernel.org> <20250820180428.592367294@kernel.org> <0d877e6f-41a7-4724-875d-0b0a27b8a545@roeck-us.net> <20260126120553.2fa79048@gandalf.local.home> <20260126121803.4a90c959@gandalf.local.home> <27f9a957-67c7-4c88-b320-0f8725e9b03d@roeck-us.net> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspamout06 X-Rspamd-Queue-Id: 56F3D2D X-Stat-Signature: y3dht6s46cac557phezgp57ms64ubspr X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+sMSEd3/nbnTD7cCLRgruhuMiDCGUh7no= X-HE-Tag: 1769527349-467222 X-HE-Meta: U2FsdGVkX19wi/5GZpUyP+BSQqWhDYL1T8dLa8uCE/dr9JD+jG8FrH4NY/oBVpREvELdR+pwpbkOCwYRHXdEsBbcLLLL9JK6ggA3qt7XtISl0TjDmR/QlsXYbUxXpqHpZ+WRaUIejWaeYKdeT8f4404wgwewi04i8n099PiYGuo0ZH82lI5Y0zVTUGe38P7B8cfeSBrQiqp26M++DmKtmzzYHPJ2gfuxQi2nUMcQZJVMe/fYkQ1AjiVDKIs2U7PQoLkecNqnRhVxiAOUQdf62aGZdGeHJQMT//TmszS9OELshDiZw/ATy+pzUestxrsyOo6dnF+OkmV/UUcWXzlogFWrVT+ObvGS31OFUkKvspcvpw+IqhhhTif/XJRC5AljdNfzuHPgrzcrZFC23q7tK43hBlsegpo3u+C1UNw12QVVdhlWK97glND0jPaGku7QbRCcnS2oBR+ELzp3G9ogeA== On Mon, 26 Jan 2026 17:32:35 -0800 Guenter Roeck wrote: > Still crashing, though not as often and with a slightly different backtrace. > I added the backtrace to the bug report @ Google. I figured there would be other locations. A while ago I had a patch to wrap the checks in a "is_user_thread()" helper function[1], but Ingo had issues with it. It seems now it's biting us in the butt and let's see if it would help now. I modified it slightly. [1] https://lore.kernel.org/linux-trace-kernel/20250425204313.616425861@goodmis.org/ If the below fixes it, I'll resend it, but now as a real bug fix. -- Steve diff --git a/include/linux/sched.h b/include/linux/sched.h index da0133524d08..5f00b5ed0f3b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1776,6 +1776,11 @@ static __always_inline bool is_percpu_thread(void) (current->nr_cpus_allowed == 1); } +static __always_inline bool is_user_task(struct task_struct *task) +{ + return task->mm && !(task->flags & (PF_KTHREAD | PF_USER_WORKER)); +} + /* Per-process atomic flags. */ #define PFA_NO_NEW_PRIVS 0 /* May not gain new privileges. */ #define PFA_SPREAD_PAGE 1 /* Spread page cache over cpuset */ diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 1f6589578703..9d24b6e0c91f 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -246,7 +246,7 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, if (user && !crosstask) { if (!user_mode(regs)) { - if (current->flags & (PF_KTHREAD | PF_USER_WORKER)) + if (!is_user_task(current)) goto exit_put; regs = task_pt_regs(current); } diff --git a/kernel/events/core.c b/kernel/events/core.c index a0fa488bce84..8cca80094624 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7460,7 +7460,7 @@ static void perf_sample_regs_user(struct perf_regs *regs_user, if (user_mode(regs)) { regs_user->abi = perf_reg_abi(current); regs_user->regs = regs; - } else if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) { + } else if (is_user_task(current)) { perf_get_regs_user(regs_user, regs); } else { regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE; @@ -8100,7 +8100,7 @@ static u64 perf_virt_to_phys(u64 virt) * Try IRQ-safe get_user_page_fast_only first. * If failed, leave phys_addr as 0. */ - if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) { + if (is_user_task(current)) { struct page *p; pagefault_disable(); @@ -8215,7 +8215,7 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) { bool kernel = !event->attr.exclude_callchain_kernel; bool user = !event->attr.exclude_callchain_user && - !(current->flags & (PF_KTHREAD | PF_USER_WORKER)); + is_user_task(current); /* Disallow cross-task user callchains. */ bool crosstask = event->ctx->task && event->ctx->task != current; bool defer_user = IS_ENABLED(CONFIG_UNWIND_USER) && user &&