[for-next][PATCH 0/8] tracing: Last minute fixes for 6.2

[for-next][PATCH 0/8] tracing: Last minute fixes for 6.2

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace/for-next

Head SHA1: 9a2179ff02e179a866375bd6916f761381749b5b


Guilherme G. Piccoli (1):
      tracing: Improve panic/die notifiers

Steven Rostedt (Google) (5):
      x86/mm/kmmio: Remove redundant preempt_disable()
      tracing: Have trigger filter parsing errors show up in error_log
      tracing: Remove pointer (asterisk) and brackets from cpumask_t field
      tracing: Do not synchronize freeing of trigger filter on boot up
      tracing: Fix cpumask() example typo

Yang Jihong (1):
      tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line

gpiccoli@igalia.com (1):
      ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

----
 arch/x86/mm/kmmio.c                        | 13 +++---
 include/trace/stages/stage4_event_fields.h | 10 ++++-
 kernel/trace/ftrace.c                      |  1 +
 kernel/trace/trace.c                       | 70 +++++++++++++++++-------------
 kernel/trace/trace_events_trigger.c        | 19 ++++++--
 samples/trace_events/trace-events-sample.h |  2 +-
 6 files changed, 72 insertions(+), 43 deletions(-)

[for-next][PATCH 1/8] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line

[Steven Rostedt]

From: Yang Jihong <yangjihong1@huawei.com>

print_trace_line may overflow seq_file buffer. If the event is not
consumed, the while loop keeps peeking this event, causing a infinite loop.

Link: https://lkml.kernel.org/r/20221129113009.182425-1-yangjihong1@huawei.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 088b1e427dbba ("ftrace: pipe fixes")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 664619b3f1e1..548890c7c0f5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6802,7 +6802,20 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
 		ret = print_trace_line(iter);
 		if (ret == TRACE_TYPE_PARTIAL_LINE) {
-			/* don't print partial lines */
+			/*
+			 * If one print_trace_line() fills entire trace_seq in one shot,
+			 * trace_seq_to_user() will returns -EBUSY because save_len == 0,
+			 * In this case, we need to consume it, otherwise, loop will peek
+			 * this event next time, resulting in an infinite loop.
+			 */
+			if (save_len == 0) {
+				iter->seq.full = 0;
+				trace_seq_puts(&iter->seq, "[LINE TOO BIG]\n");
+				trace_consume(iter);
+				break;
+			}
+
+			/* In other cases, don't print partial lines */
 			iter->seq.seq.len = save_len;
 			break;
 		}
-- 
2.35.1

[for-next][PATCH 2/8] x86/mm/kmmio: Remove redundant preempt_disable()

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Now that kmmio uses rcu_read_lock_sched_notrace() there's no reason to
call preempt_disable() as the read_lock_sched_notrace() already does that
and is redundant.

This also removes the preempt_enable_no_resched() as the "no_resched()"
portion was bogus as there's no reason to do that.

Link: https://lkml.kernel.org/r/20221212103703.7129cc5d@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "x86@kernel.org" <x86@kernel.org>
Cc: Karol Herbst <karolherbst@gmail.com>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 arch/x86/mm/kmmio.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index 853c49877c16..9f82019179e1 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -246,14 +246,13 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr)
 	page_base &= page_level_mask(l);
 
 	/*
-	 * Preemption is now disabled to prevent process switch during
-	 * single stepping. We can only handle one active kmmio trace
+	 * Hold the RCU read lock over single stepping to avoid looking
+	 * up the probe and kmmio_fault_page again. The rcu_read_lock_sched()
+	 * also disables preemption and prevents process switch during
+	 * the single stepping. We can only handle one active kmmio trace
 	 * per cpu, so ensure that we finish it before something else
-	 * gets to run. We also hold the RCU read lock over single
-	 * stepping to avoid looking up the probe and kmmio_fault_page
-	 * again.
+	 * gets to run.
 	 */
-	preempt_disable();
 	rcu_read_lock_sched_notrace();
 
 	faultpage = get_kmmio_fault_page(page_base);
@@ -324,7 +323,6 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr)
 
 no_kmmio:
 	rcu_read_unlock_sched_notrace();
-	preempt_enable_no_resched();
 	return ret;
 }
 
@@ -364,7 +362,6 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
 	ctx->active--;
 	BUG_ON(ctx->active);
 	rcu_read_unlock_sched_notrace();
-	preempt_enable_no_resched();
 
 	/*
 	 * if somebody else is singlestepping across a probe point, flags
-- 
2.35.1

[for-next][PATCH 3/8] tracing: Have trigger filter parsing errors show up in error_log

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

It is annoying that the filter parsing of triggers do not show up in the
error_log. Trying to figure out what is incorrect in the input is
difficult when it fails for a typo.

Have the errors of filter parsing show up in error_log as well.

Link: https://lore.kernel.org/linux-trace-kernel/20221213095602.083fa9fd@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_events_trigger.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 918730d74932..19ce9d22bfd7 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1067,7 +1067,14 @@ int set_trigger_filter(char *filter_str,
 
 	/* The filter is for the 'trigger' event, not the triggered event */
 	ret = create_event_filter(file->tr, file->event_call,
-				  filter_str, false, &filter);
+				  filter_str, true, &filter);
+
+	/* Only enabled set_str for error handling */
+	if (filter) {
+		kfree(filter->filter_string);
+		filter->filter_string = NULL;
+	}
+
 	/*
 	 * If create_event_filter() fails, filter still needs to be freed.
 	 * Which the calling code will do with data->filter.
-- 
2.35.1

[for-next][PATCH 4/8] tracing: Remove pointer (asterisk) and brackets from cpumask_t field

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

To differentiate between long arrays and cpumasks, the __cpumask() field
was created. Part of the TRACE_EVENT() macros test if the type is signed
or not by using the is_signed_type() macro. The __cpumask() field used the
__dynamic_array() helper but because cpumask_t is a structure, it could
not be used in the is_signed_type() macro as that would fail to build, so
instead it passed in the pointer to cpumask_t.

Unfortunately, that creates in the format file:

  field:__data_loc cpumask_t *[] mask;    offset:36;      size:4; signed:0;

Which looks like an array of pointers to cpumask_t and not a cpumask_t
type, which is misleading to user space parsers.

Douglas Raillard pointed out that the "[]" are also misleading, as
cpumask_t is not an array.

Since cpumask() hasn't been created yet, and the parsers currently fail on
it (but will still produce the raw output), make it be:

  field:__data_loc cpumask_t mask;    offset:36;      size:4; signed:0;

Which is the correct type of the field.

Then the parsers can be updated to handle this.

Link: https://lore.kernel.org/lkml/6dda5e1d-9416-b55e-88f3-31d148bc925f@arm.com/
Link: https://lore.kernel.org/linux-trace-kernel/20221212193814.0e3f1e43@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 8230f27b1ccc ("tracing: Add __cpumask to denote a trace event field that is a cpumask_t")
Reported-by: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/trace/stages/stage4_event_fields.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/trace/stages/stage4_event_fields.h b/include/trace/stages/stage4_event_fields.h
index f2990d22313c..affd541fd25e 100644
--- a/include/trace/stages/stage4_event_fields.h
+++ b/include/trace/stages/stage4_event_fields.h
@@ -47,7 +47,10 @@
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 
 #undef __cpumask
-#define __cpumask(item) __dynamic_array(cpumask_t *, item, -1)
+#define __cpumask(item) {						\
+	.type = "__data_loc cpumask_t", .name = #item,			\
+	.size = 4, .align = 4,						\
+	.is_signed = 0, .filter_type = FILTER_OTHER },
 
 #undef __sockaddr
 #define __sockaddr(field, len) __dynamic_array(u8, field, len)
@@ -68,7 +71,10 @@
 #define __rel_bitmask(item, nr_bits) __rel_dynamic_array(unsigned long, item, -1)
 
 #undef __rel_cpumask
-#define __rel_cpumask(item) __rel_dynamic_array(cpumask_t *, item, -1)
+#define __rel_cpumask(item) {						\
+	.type = "__rel_loc cpumask_t", .name = #item,			\
+	.size = 4, .align = 4,						\
+	.is_signed = 0, .filter_type = FILTER_OTHER },
 
 #undef __rel_sockaddr
 #define __rel_sockaddr(field, len) __rel_dynamic_array(u8, field, len)
-- 
2.35.1

[for-next][PATCH 5/8] tracing: Do not synchronize freeing of trigger filter on boot up

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

If a trigger filter on the kernel command line fails to apply (due to
syntax error), it will be freed. The freeing will call
tracepoint_synchronize_unregister(), but this is not needed during early
boot up, and will even trigger a lockdep splat.

Avoid calling the synchronization function when system_state is
SYSTEM_BOOTING.

Link: https://lore.kernel.org/linux-trace-kernel/20221213172429.7774f4ba@gandalf.local.home

Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_events_trigger.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 19ce9d22bfd7..e535959939d3 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1085,8 +1085,14 @@ int set_trigger_filter(char *filter_str,
 	rcu_assign_pointer(data->filter, filter);
 
 	if (tmp) {
-		/* Make sure the call is done with the filter */
-		tracepoint_synchronize_unregister();
+		/*
+		 * Make sure the call is done with the filter.
+		 * It is possible that a filter could fail at boot up,
+		 * and then this path will be called. Avoid the synchronization
+		 * in that case.
+		 */
+		if (system_state != SYSTEM_BOOTING)
+			tracepoint_synchronize_unregister();
 		free_event_filter(tmp);
 	}
 
-- 
2.35.1

[for-next][PATCH 6/8] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

[Steven Rostedt]

From: "gpiccoli@igalia.com" <gpiccoli@igalia.com>

The function match_records() may take a while due to a large
number of string comparisons, so when in PREEMPT_VOLUNTARY
kernels we could face RCU stalls due to that.

Add a cond_resched() to prevent that.

Link: https://lkml.kernel.org/r/20221115204847.593616-1-gpiccoli@igalia.com

Cc: Mark Rutland <mark.rutland@arm.com>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d04552c0c275..b8e374a372e5 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4204,6 +4204,7 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
 			}
 			found = 1;
 		}
+		cond_resched();
 	} while_for_each_ftrace_rec();
  out_unlock:
 	mutex_unlock(&ftrace_lock);
-- 
2.35.1

[for-next][PATCH 7/8] tracing: Improve panic/die notifiers

[Steven Rostedt]

From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>

Currently the tracing dump_on_oops feature is implemented through
separate notifiers, one for die/oops and the other for panic;
given they have the same functionality, let's unify them.

Also improve the function comment and change the priority of the
notifier to make it execute earlier, avoiding showing useless trace
data (like the callback names for the other notifiers); finally,
we also removed an unnecessary header inclusion.

Link: https://lkml.kernel.org/r/20220819221731.480795-7-gpiccoli@igalia.com

Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergei Shtylyov <sergei.shtylyov@gmail.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 55 ++++++++++++++++++++++----------------------
 1 file changed, 27 insertions(+), 28 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 548890c7c0f5..6d7ef130f57e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -19,7 +19,6 @@
 #include <linux/kallsyms.h>
 #include <linux/security.h>
 #include <linux/seq_file.h>
-#include <linux/notifier.h>
 #include <linux/irqflags.h>
 #include <linux/debugfs.h>
 #include <linux/tracefs.h>
@@ -9876,40 +9875,40 @@ static __init int tracer_init_tracefs(void)
 
 fs_initcall(tracer_init_tracefs);
 
-static int trace_panic_handler(struct notifier_block *this,
-			       unsigned long event, void *unused)
-{
-	if (ftrace_dump_on_oops)
-		ftrace_dump(ftrace_dump_on_oops);
-	return NOTIFY_OK;
-}
+static int trace_die_panic_handler(struct notifier_block *self,
+				unsigned long ev, void *unused);
 
 static struct notifier_block trace_panic_notifier = {
-	.notifier_call  = trace_panic_handler,
-	.next           = NULL,
-	.priority       = 150   /* priority: INT_MAX >= x >= 0 */
+	.notifier_call = trace_die_panic_handler,
+	.priority = INT_MAX - 1,
 };
 
-static int trace_die_handler(struct notifier_block *self,
-			     unsigned long val,
-			     void *data)
-{
-	switch (val) {
-	case DIE_OOPS:
-		if (ftrace_dump_on_oops)
-			ftrace_dump(ftrace_dump_on_oops);
-		break;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
 static struct notifier_block trace_die_notifier = {
-	.notifier_call = trace_die_handler,
-	.priority = 200
+	.notifier_call = trace_die_panic_handler,
+	.priority = INT_MAX - 1,
 };
 
+/*
+ * The idea is to execute the following die/panic callback early, in order
+ * to avoid showing irrelevant information in the trace (like other panic
+ * notifier functions); we are the 2nd to run, after hung_task/rcu_stall
+ * warnings get disabled (to prevent potential log flooding).
+ */
+static int trace_die_panic_handler(struct notifier_block *self,
+				unsigned long ev, void *unused)
+{
+	if (!ftrace_dump_on_oops)
+		return NOTIFY_DONE;
+
+	/* The die notifier requires DIE_OOPS to trigger */
+	if (self == &trace_die_notifier && ev != DIE_OOPS)
+		return NOTIFY_DONE;
+
+	ftrace_dump(ftrace_dump_on_oops);
+
+	return NOTIFY_DONE;
+}
+
 /*
  * printk is set to max of 1024, we really don't need it that big.
  * Nothing should be printing 1000 characters anyway.
-- 
2.35.1

[for-next][PATCH 8/8] tracing: Fix cpumask() example typo

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The sample code for using cpumask used the wrong field for the
__get_cpumask() helper. It used "cpus" which is the bitmask (but would
still give a proper example) instead of the "cpum" that was there to be
used.

Although it produces the same output, fix it, because it's an example and
is confusing in how to properly use the cpumask() macro.

Link: https://lore.kernel.org/linux-trace-kernel/20221213221227.56560374@gandalf.local.home

Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 samples/trace_events/trace-events-sample.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index fb4548a44153..1c6b843b8c4e 100644
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -359,7 +359,7 @@ TRACE_EVENT(foo_bar,
 		  __print_array(__get_dynamic_array(list),
 				__get_dynamic_array_len(list) / sizeof(int),
 				sizeof(int)),
-		  __get_str(str), __get_bitmask(cpus), __get_cpumask(cpus),
+		  __get_str(str), __get_bitmask(cpus), __get_cpumask(cpum),
 		  __get_str(vstr))
 );
 
-- 
2.35.1

Re: [for-next][PATCH 6/8] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

[Guilherme G. Piccoli]

On 14/12/2022 11:01, Steven Rostedt wrote:
> From: "gpiccoli@igalia.com" <gpiccoli@igalia.com>

Hi Steve, would be possible to use my full name here, like: Guilherme G.
Piccoli <gpiccoli@igalia.com> ?

Thanks,


Guilherme

> 
> The function match_records() may take a while due to a large
> number of string comparisons, so when in PREEMPT_VOLUNTARY
> kernels we could face RCU stalls due to that.
> 
> Add a cond_resched() to prevent that.
> 
> Link: https://lkml.kernel.org/r/20221115204847.593616-1-gpiccoli@igalia.com
> 
> Cc: Mark Rutland <mark.rutland@arm.com>
> Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/ftrace.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index d04552c0c275..b8e374a372e5 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4204,6 +4204,7 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
>  			}
>  			found = 1;
>  		}
> +		cond_resched();
>  	} while_for_each_ftrace_rec();
>   out_unlock:
>  	mutex_unlock(&ftrace_lock);

Re: [for-next][PATCH 6/8] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

[Steven Rostedt]

On Wed, 14 Dec 2022 12:53:04 -0300
"Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote:

> On 14/12/2022 11:01, Steven Rostedt wrote:
> > From: "gpiccoli@igalia.com" <gpiccoli@igalia.com>  
> 
> Hi Steve, would be possible to use my full name here, like: Guilherme G.
> Piccoli <gpiccoli@igalia.com> ?

Sure, I haven't pushed to the next repo yet.

I found the reason it didn't go into my patchwork, and did a resend via a
"redirect", and that must have changed the from address :-/

-- Steve

Re: [for-next][PATCH 6/8] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

[Steven Rostedt]

On Wed, 14 Dec 2022 11:15:44 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 14 Dec 2022 12:53:04 -0300
> "Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote:
> 
> > On 14/12/2022 11:01, Steven Rostedt wrote:  
> > > From: "gpiccoli@igalia.com" <gpiccoli@igalia.com>    
> > 
> > Hi Steve, would be possible to use my full name here, like: Guilherme G.
> > Piccoli <gpiccoli@igalia.com> ?  
> 
> Sure, I haven't pushed to the next repo yet.
> 
> I found the reason it didn't go into my patchwork, and did a resend via a
> "redirect", and that must have changed the from address :-/
> 

Here's the new update:

-- Steve


From d0b24b4e91fcb8408c4979888547f86be514e337 Mon Sep 17 00:00:00 2001
From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Date: Tue, 15 Nov 2022 17:48:47 -0300
Subject: [PATCH] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

The function match_records() may take a while due to a large
number of string comparisons, so when in PREEMPT_VOLUNTARY
kernels we could face RCU stalls due to that.

Add a cond_resched() to prevent that.

Link: https://lkml.kernel.org/r/20221115204847.593616-1-gpiccoli@igalia.com

Cc: Mark Rutland <mark.rutland@arm.com>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org> # from RCU CPU stall warning perspective
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d04552c0c275..b8e374a372e5 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4204,6 +4204,7 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
 			}
 			found = 1;
 		}
+		cond_resched();
 	} while_for_each_ftrace_rec();
  out_unlock:
 	mutex_unlock(&ftrace_lock);
-- 
2.35.1

Re: [for-next][PATCH 6/8] ftrace: Prevent RCU stall on PREEMPT_VOLUNTARY kernels

[Guilherme G. Piccoli]

On 14/12/2022 13:15, Steven Rostedt wrote:
> On Wed, 14 Dec 2022 12:53:04 -0300
> "Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote:
> 
>> On 14/12/2022 11:01, Steven Rostedt wrote:
>>> From: "gpiccoli@igalia.com" <gpiccoli@igalia.com>  
>>
>> Hi Steve, would be possible to use my full name here, like: Guilherme G.
>> Piccoli <gpiccoli@igalia.com> ?
> 
> Sure, I haven't pushed to the next repo yet.
> 
> I found the reason it didn't go into my patchwork, and did a resend via a
> "redirect", and that must have changed the from address :-/
> 
> -- Steve

Perfect, thanks a lot for your prompt response!!