From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 050F918130D; Tue, 29 Oct 2024 18:10:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730225421; cv=none; b=Ime6slyI2IvkVmRnXngEG8ulMRwpYK8XN0Qe4QYgI/BqkDk5enIXKKqhEZN8KFIc6LLjE5fS0YOwjpSn/f7njsao/ixQGQsDAoAxZQMbgb/j4rbJVYOW2srdEaHBwbtCMwAJ3oaTS0HUwtrmpQ8nHWdCjl3dGm9uXzIUaUevfOM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730225421; c=relaxed/simple; bh=rSEPCwo3+FNPhGsdt6dt/oTNiBavhSDE5Kcuve0mHNQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EAXowjSnxIVXJT1u9lIn+KWq/ZdoVdS88jr9Elk/lAw1DrHAVa2B2HOw+6pv6Hom8+0h9ZlRKgIHTG/JuocLgBxg8rNcWrbBUdUeGJSTfFxI7vC9QRLqUyjiK62aLLVkTnTJvlnq1GA+4pofq9RrFe/ZiajZ8N9v+sXmruBO/Mg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=IYV4OxWf; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IYV4OxWf" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4RFd0kI+7YFYqaFoPNrQ859Edbrzs6npcu3fCsS77ac=; b=IYV4OxWfDSGXniyTxmIA+Nqksi hfZn8Oc3qb8GtSkRZU0K7BEIlHRG/TensNiDi2gV892TFHRMPcJD6EYSCENxkvSK1Nbr1VSxvb2rX KkuXw5pESy/mFQO2wPPs6mrUcwUbVvAKdcxUDoYqmuEA9b+UCQ13AF5P1XY1WGQclSRugUjN4qTj1 3FebFZCqrrj4s1qNBKRqqD4SZXMB/3+YUcMHy9OqkRn6zvawxuZ1uiyILgTnkQoDq6M7c8ihtqj4b 9Tx0+cTJ9Hv6tAUM/RPEVkNhuOI4GeVa+EyKTNn5+4++IURZPYhKQNiIlYmAwhz3WDWYJnWZLU2Ba dCz7KS5A==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1t5qfQ-0000000ABZ4-1mBv; Tue, 29 Oct 2024 18:10:09 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id AA8FF30073F; Tue, 29 Oct 2024 19:10:08 +0100 (CET) Date: Tue, 29 Oct 2024 19:10:08 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: x86@kernel.org, Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Indu Bhagat , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, Mark Brown , linux-toolchains@vger.kernel.org, Jordan Rome , Sam James , linux-trace-kernel@vger.kerne.org, Andrii Nakryiko , Jens Remus , Mathieu Desnoyers , Florian Weimer , Andy Lutomirski Subject: Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding Message-ID: <20241029181008.GG14555@noisy.programming.kicks-ass.net> References: <42c0a99236af65c09c8182e260af7bcf5aa1e158.1730150953.git.jpoimboe@kernel.org> <20241029132709.GY14555@noisy.programming.kicks-ass.net> <20241029165018.r4l5wix24s3f22c6@treble.attlocal.net> 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-Disposition: inline In-Reply-To: <20241029165018.r4l5wix24s3f22c6@treble.attlocal.net> On Tue, Oct 29, 2024 at 09:50:18AM -0700, Josh Poimboeuf wrote: > On Tue, Oct 29, 2024 at 02:27:09PM +0100, Peter Zijlstra wrote: > > > +int sframe_add_section(unsigned long sframe_addr, unsigned long text_start, > > > + unsigned long text_end) > > > +{ > > > + struct mm_struct *mm = current->mm; > > > + struct vm_area_struct *sframe_vma; > > > + > > > + mmap_read_lock(mm); > > > > DEFINE_GUARD(mmap_read_lock, struct mm_struct *, > > mmap_read_lock(_T), mmap_read_unlock(_T)) > > > > in include/linux/mmap_lock.h ? > > Will do. > > > > @@ -2784,6 +2785,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > > > case PR_RISCV_SET_ICACHE_FLUSH_CTX: > > > error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3); > > > break; > > > + case PR_ADD_SFRAME: > > > + if (arg5) > > > + return -EINVAL; > > > + error = sframe_add_section(arg2, arg3, arg4); > > > + break; > > > + case PR_REMOVE_SFRAME: > > > + if (arg3 || arg4 || arg5) > > > + return -EINVAL; > > > + error = sframe_remove_section(arg2); > > > + break; > > > default: > > > error = -EINVAL; > > > break; > > > > So I realize that mtree has an internal lock, but are we sure we don't > > want a lock around those prctl()s? > > Not that I can tell? It relies on the mtree internal locking for > atomicity. > > For sframe_remove_section() it uses srcu to delay the freeing until all > sframe_find()'s have completed. Yeah it does all that. But I was sorta looking at all that kmalloc and copy from user stuff, but I suppose you can race that without problem.