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 71EB0824BD; Thu, 3 Oct 2024 22:28:42 +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=1727994522; cv=none; b=ikPP0IXFi1M+HW39W49156lVTdO19ETynP9QsS8xb3nBUlB1+DLBoRZMsiuLZj8c65ApWGmHAQRvMsn7aGpogvRTwVZMQa7ZFeUV/cKTI1IUh8nN86dpmsbb/HIhqvjc5ercgi/LDFvddox+QLrxqaj19x+sTbB6PJoyxS/RcCE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727994522; c=relaxed/simple; bh=vQ+Gtq2rZ0DxAhxXGoKR2qzo/BAO0lltv5yXC5hj17o=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=DnG1OS9aiu9+5Bg5OhkspSvL+WLMM8Gwd3JBsAK/6+7pzaL3nj61S4bUpjmxGtuFo2JEGf6lafjzkMk40/c8GzVEHBjKNvHynDLbN+IuV0SIMgQrPzZpOxs7UDmpRPu5Y0qFUWmlbw4BAmW+yNi9reRudG6Ol1DYgsEOQHxuxtE= 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 26477C4CEC5; Thu, 3 Oct 2024 22:28:40 +0000 (UTC) Date: Thu, 3 Oct 2024 18:29:34 -0400 From: Steven Rostedt To: Mathieu Desnoyers Cc: Masami Hiramatsu , linux-kernel@vger.kernel.org, Peter Zijlstra , Alexei Starovoitov , Yonghong Song , "Paul E . McKenney" , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Namhyung Kim , Andrii Nakryiko , bpf@vger.kernel.org, Joel Fernandes , linux-trace-kernel@vger.kernel.org, Michael Jeanson Subject: Re: [PATCH v1 5/8] tracing: Allow system call tracepoints to handle page faults Message-ID: <20241003182934.0a027919@gandalf.local.home> In-Reply-To: <20241003151638.1608537-6-mathieu.desnoyers@efficios.com> References: <20241003151638.1608537-1-mathieu.desnoyers@efficios.com> <20241003151638.1608537-6-mathieu.desnoyers@efficios.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 Thu, 3 Oct 2024 11:16:35 -0400 Mathieu Desnoyers wrote: > Use Tasks Trace RCU to protect iteration of system call enter/exit > tracepoint probes to allow those probes to handle page faults. > > In preparation for this change, all tracers registering to system call > enter/exit tracepoints should expect those to be called with preemption > enabled. > > This allows tracers to fault-in userspace system call arguments such as > path strings within their probe callbacks. > > Signed-off-by: Mathieu Desnoyers > Cc: Michael Jeanson > Cc: Steven Rostedt > Cc: Masami Hiramatsu > Cc: Peter Zijlstra > Cc: Alexei Starovoitov > Cc: Yonghong Song > Cc: Paul E. McKenney > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Mark Rutland > Cc: Alexander Shishkin > Cc: Namhyung Kim > Cc: Andrii Nakryiko > Cc: bpf@vger.kernel.org > Cc: Joel Fernandes > --- > include/linux/tracepoint.h | 25 +++++++++++++++++-------- > init/Kconfig | 1 + > 2 files changed, 18 insertions(+), 8 deletions(-) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 666499b9f3be..6faf34e5efc9 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -17,6 +17,7 @@ > #include > #include > #include > +#include > #include > #include > > @@ -109,6 +110,7 @@ void for_each_tracepoint_in_module(struct module *mod, > #ifdef CONFIG_TRACEPOINTS > static inline void tracepoint_synchronize_unregister(void) > { > + synchronize_rcu_tasks_trace(); > synchronize_srcu(&tracepoint_srcu); > synchronize_rcu(); > } > @@ -211,7 +213,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > * it_func[0] is never NULL because there is at least one element in the array > * when the array itself is non NULL. > */ > -#define __DO_TRACE(name, args, cond, rcuidle) \ > +#define __DO_TRACE(name, args, cond, rcuidle, syscall) \ > do { \ > int __maybe_unused __idx = 0; \ > \ > @@ -222,8 +224,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > "Bad RCU usage for tracepoint")) \ > return; \ > \ > - /* keep srcu and sched-rcu usage consistent */ \ > - preempt_disable_notrace(); \ > + if (syscall) { \ > + rcu_read_lock_trace(); \ > + } else { \ > + /* keep srcu and sched-rcu usage consistent */ \ > + preempt_disable_notrace(); \ > + } \ > \ I'm thinking we just use rcu_read_lock_trace() and get rid of the preempt_disable and srcu locks for all tracepoints. Oh crap! I should get rid of srcu locking too, as it was only needed for the rcuidle code :-p -- Steve > /* \ > * For rcuidle callers, use srcu since sched-rcu \ > @@ -241,7 +247,10 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\ > } \ > \ > - preempt_enable_notrace(); \ > + if (syscall) \ > + rcu_read_unlock_trace(); \ > + else \ > + preempt_enable_notrace(); \ > } while (0) > > #ifndef MODULE > @@ -251,7 +260,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > if (static_key_false(&__tracepoint_##name.key)) \ > __DO_TRACE(name, \ > TP_ARGS(args), \ > - TP_CONDITION(cond), 1); \ > + TP_CONDITION(cond), 1, 0); \ > } > #else > #define __DECLARE_TRACE_RCU(name, proto, args, cond) > @@ -284,7 +293,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > if (static_key_false(&__tracepoint_##name.key)) \ > __DO_TRACE(name, \ > TP_ARGS(args), \ > - TP_CONDITION(cond), 0); \ > + TP_CONDITION(cond), 0, 0); \ > if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \ > WARN_ONCE(!rcu_is_watching(), \ > "RCU not watching for tracepoint"); \ > @@ -295,7 +304,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > if (static_key_false(&__tracepoint_##name.key)) \ > __DO_TRACE(name, \ > TP_ARGS(args), \ > - TP_CONDITION(cond), 1); \ > + TP_CONDITION(cond), 1, 0); \ > } \ > static inline int \ > register_trace_##name(void (*probe)(data_proto), void *data) \ > @@ -330,7 +339,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > if (static_key_false(&__tracepoint_##name.key)) \ > __DO_TRACE(name, \ > TP_ARGS(args), \ > - TP_CONDITION(cond), 0); \ > + TP_CONDITION(cond), 0, 1); \ > if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \ > WARN_ONCE(!rcu_is_watching(), \ > "RCU not watching for tracepoint"); \ > diff --git a/init/Kconfig b/init/Kconfig > index fbd0cb06a50a..eedd0064fb36 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1984,6 +1984,7 @@ config BINDGEN_VERSION_TEXT > # > config TRACEPOINTS > bool > + select TASKS_TRACE_RCU > > source "kernel/Kconfig.kexec" >