From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1CDA63B791 for ; Fri, 20 Dec 2024 15:05:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734707118; cv=none; b=IxWvN/mAbR6gCOw5hv7BQGp5A4efXkVJ+BRZoDOgzT/21dZ+vPC7rBBwDqPW4UI3zoocBAdj9+gGkt47JoB9HgwGXIPIET9Ov7ars8pCeT0/EO+pq/pfYf5FV2axQonqxWMBwMT95Yrr0ya1FOTNYy7AJall27tbwD/ie5ujWp4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734707118; c=relaxed/simple; bh=Hq27cTk+WIA+qmH+p2nx5m6QcmAqoYPQ5zoBPaG/8Es=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KZBHUbHBtLKzP1SLCDyCQhZq2QqcnqoASWV2ISL5ItNftNH2DOgDZaNxoTMFr7j4oXXKYO4b4U8v45+1s1hUvlsXxw4ujkLk08+VA/AP7luMnst8mw6rG1/FbHfrkeuIhBaka2QYvptKJXiGHbrOC90CQz812cPK9aXipcsO5X4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id F13EBC4CECD; Fri, 20 Dec 2024 15:05:15 +0000 (UTC) Date: Fri, 20 Dec 2024 10:05:58 -0500 From: Steven Rostedt To: Ludwig Rydberg Cc: linux-trace-kernel@vger.kernel.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, Andreas Larsson Subject: Re: [BUG] spinlock recursion when enabling function tracer on 32-bit Message-ID: <20241220100558.10b48f0f@gandalf.local.home> In-Reply-To: <2d634c54-d8d9-4f33-bfda-9236b6a2ea06@gaisler.com> References: <86fb4f86-a0e4-45a2-a2df-3154acc4f086@gaisler.com> <20241218110115.29d4cc77@gandalf.local.home> <20241218163526.2569917f@gandalf.local.home> <2d634c54-d8d9-4f33-bfda-9236b6a2ea06@gaisler.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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-Transfer-Encoding: 7bit On Fri, 20 Dec 2024 14:55:27 +0100 Ludwig Rydberg wrote: > On 2024-12-18 22:35, Steven Rostedt wrote: > > > > > Can you test this patch? > > > > I have tested the patch on both riscv32 (qemu) & sparc32 (leon) and it seems > to be working fine. > > But I can mention that I ran into a deadlock situation on sparc32. > I had to remove CC_FLAGS_FTRACE for the code that is responsible for > flushing TLBs (SMP). It uses an NMI to signal other CPUs which triggered > the deadlock if tracing was enabled on that path. Can you try this patch on top of the last one? -- Steve diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 7e257e855dd1..a9fe54b79ce5 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4398,8 +4398,13 @@ rb_reserve_next_event(struct trace_buffer *buffer, int nr_loops = 0; int add_ts_default; - /* ring buffer does cmpxchg, make sure it is safe in NMI context */ - if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && + /* + * ring buffer does cmpxchg as well as atomic64 operations + * (which some archs use locking for atomic64), make sure this + * is safe in NMI context + */ + if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) || + IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) && (unlikely(in_nmi()))) { return NULL; }