From: Peter Zijlstra <peterz@infradead.org>
To: 王贇 <yun.wang@linux.alibaba.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
open list <linux-kernel@vger.kernel.org>,
Jiri Olsa <jolsa@redhat.com>
Subject: Re: [RESEND PATCH v2] trace: prevent preemption in perf_ftrace_function_call()
Date: Mon, 11 Oct 2021 10:32:46 +0200 [thread overview]
Message-ID: <YWP2rtX9Ol9dZc/l@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <bcdbccc6-a516-2199-d3be-090a5e9f601d@linux.alibaba.com>
On Mon, Oct 11, 2021 at 10:38:39AM +0800, 王贇 wrote:
>
>
> On 2021/10/9 上午8:03, Steven Rostedt wrote:
> > On Tue, 28 Sep 2021 11:12:24 +0800
> > 王贇 <yun.wang@linux.alibaba.com> wrote:
> >
> >> With CONFIG_DEBUG_PREEMPT we observed reports like:
> >>
> >> BUG: using smp_processor_id() in preemptible
> >> caller is perf_ftrace_function_call+0x6f/0x2e0
> >> CPU: 1 PID: 680 Comm: a.out Not tainted
> >> Call Trace:
> >> <TASK>
> >> dump_stack_lvl+0x8d/0xcf
> >> check_preemption_disabled+0x104/0x110
> >> ? optimize_nops.isra.7+0x230/0x230
> >> ? text_poke_bp_batch+0x9f/0x310
> >> perf_ftrace_function_call+0x6f/0x2e0
> >> ...
> >
> > It would be useful to see the full backtrace, to know how this
> > happened. Please do not shorten back traces.
>
> Here it is, I suppose some where on the path of __text_poke failed to
> exempt from ftrace, whose context is allowed to be preempted?
Urgh, 'funny' trace that... it ends up tracing text_poke while it's
installing the ftrace handlers.
But no, that looks quite all right.
Your patch is also right, I think, except we can improve upon it by
having that recursion_trylock imply preemption disable (as is proper for
a 'lock').
Also, make sure to disable preemption before, and enable it after,
taking, or releasing, the lock. That way we don't have preemption holes.
---
arch/csky/kernel/probes/ftrace.c | 2 --
arch/parisc/kernel/ftrace.c | 2 --
arch/powerpc/kernel/kprobes-ftrace.c | 2 --
arch/s390/kernel/ftrace.c | 2 --
arch/x86/kernel/kprobes/ftrace.c | 2 --
include/linux/trace_recursion.h | 10 +++++++++-
kernel/livepatch/patch.c | 6 ------
kernel/trace/trace_functions.c | 5 -----
8 files changed, 9 insertions(+), 22 deletions(-)
diff --git a/arch/csky/kernel/probes/ftrace.c b/arch/csky/kernel/probes/ftrace.c
index ef2bb9bd9605..dff7921531ef 100644
--- a/arch/csky/kernel/probes/ftrace.c
+++ b/arch/csky/kernel/probes/ftrace.c
@@ -24,7 +24,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (!p) {
p = get_kprobe((kprobe_opcode_t *)(ip - MCOUNT_INSN_SIZE));
@@ -64,7 +63,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
index 0a1e75af5382..3543496174d3 100644
--- a/arch/parisc/kernel/ftrace.c
+++ b/arch/parisc/kernel/ftrace.c
@@ -216,7 +216,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
@@ -245,7 +244,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
}
__this_cpu_write(current_kprobe, NULL);
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c
index 7154d58338cc..072ebe7f290b 100644
--- a/arch/powerpc/kernel/kprobes-ftrace.c
+++ b/arch/powerpc/kernel/kprobes-ftrace.c
@@ -26,7 +26,6 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)nip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
@@ -61,7 +60,6 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 1d94ffdf347b..fa1e3510ea98 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -367,7 +367,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
@@ -395,7 +394,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
}
__this_cpu_write(current_kprobe, NULL);
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 596de2f6d3a5..dd2ec14adb77 100644
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -25,7 +25,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
if (bit < 0)
return;
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
@@ -59,7 +58,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index a9f9c5714e65..ca12e2d8e060 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -214,7 +214,14 @@ static __always_inline void trace_clear_recursion(int bit)
static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
unsigned long parent_ip)
{
- return trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX);
+ bool ret;
+
+ preempt_disable_notrace();
+ ret = trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX);
+ if (!ret)
+ preempt_enable_notrace();
+
+ return ret;
}
/**
@@ -226,6 +233,7 @@ static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
static __always_inline void ftrace_test_recursion_unlock(int bit)
{
trace_clear_recursion(bit);
+ preempt_enable_notrace();
}
#endif /* CONFIG_TRACING */
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index e8029aea67f1..6e66ccdefaa9 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -52,11 +52,6 @@ static void notrace klp_ftrace_handler(unsigned long ip,
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (WARN_ON_ONCE(bit < 0))
return;
- /*
- * A variant of synchronize_rcu() is used to allow patching functions
- * where RCU is not watching, see klp_synchronize_transition().
- */
- preempt_disable_notrace();
func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
stack_node);
@@ -120,7 +115,6 @@ static void notrace klp_ftrace_handler(unsigned long ip,
klp_arch_set_pc(fregs, (unsigned long)func->new_func);
unlock:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 1f0e63f5d1f9..9f1bfbe105e8 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -186,7 +186,6 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
return;
trace_ctx = tracing_gen_ctx();
- preempt_disable_notrace();
cpu = smp_processor_id();
data = per_cpu_ptr(tr->array_buffer.data, cpu);
@@ -194,7 +193,6 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
trace_function(tr, ip, parent_ip, trace_ctx);
ftrace_test_recursion_unlock(bit);
- preempt_enable_notrace();
}
#ifdef CONFIG_UNWINDER_ORC
@@ -298,8 +296,6 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
if (bit < 0)
return;
- preempt_disable_notrace();
-
cpu = smp_processor_id();
data = per_cpu_ptr(tr->array_buffer.data, cpu);
if (atomic_read(&data->disabled))
@@ -324,7 +320,6 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
out:
ftrace_test_recursion_unlock(bit);
- preempt_enable_notrace();
}
static void
next prev parent reply other threads:[~2021-10-11 8:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-28 3:12 [RESEND PATCH v2] trace: prevent preemption in perf_ftrace_function_call() 王贇
2021-10-09 0:03 ` Steven Rostedt
2021-10-11 2:38 ` 王贇
2021-10-11 8:32 ` Peter Zijlstra [this message]
2021-10-11 8:48 ` Peter Zijlstra
2021-10-11 9:39 ` 王贇
2021-10-11 14:45 ` Peter Zijlstra
2021-10-12 5:51 ` 王贇
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YWP2rtX9Ol9dZc/l@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=rostedt@goodmis.org \
--cc=yun.wang@linux.alibaba.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.