On 2/14/22 3:45 AM, Daniel Bristot de Oliveira wrote:
Sample reactor that printks the reaction message.
Who is supposed to take action on this message and how do they
get notified?
Note: do not use this reactor with rq_lock taken, it will lock the
system until printk can handle that.
Please give more details on "lock the system" and how locking
would impact users and system operation
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: Gabriele Paoloni <gpaoloni@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Clark Williams <williams@xxxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-trace-devel@xxxxxxxxxxxxxxx
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
---
kernel/trace/rv/Kconfig | 8 ++++++
kernel/trace/rv/Makefile | 3 ++-
kernel/trace/rv/reactor_printk.c | 43 ++++++++++++++++++++++++++++++++
3 files changed, 53 insertions(+), 1 deletion(-)
create mode 100644 kernel/trace/rv/reactor_printk.c
diff --git a/kernel/trace/rv/Kconfig b/kernel/trace/rv/Kconfig
index f2d0bed05a55..490f1417def9 100644
--- a/kernel/trace/rv/Kconfig
+++ b/kernel/trace/rv/Kconfig
@@ -37,4 +37,12 @@ config RV_REACTORS
tracing reactions, printing the monitor output via tracepoints,
but other reactions can be added (on-demand) via this interface.
+config RV_REACT_PRINTK
+ tristate "Printk reactor"
+ depends on RV_REACTORS
+ default y if RV_REACTORS
+ help
+ Enables the printk reactor. The printk reactor emmits a printk()
+ message if an exception is found.
+
endif # RV
diff --git a/kernel/trace/rv/Makefile b/kernel/trace/rv/Makefile
index edad01bb2b5d..d86ceb103ef2 100644
--- a/kernel/trace/rv/Makefile
+++ b/kernel/trace/rv/Makefile
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_RV) += rv.o
-obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
obj-$(CONFIG_RV_MON_WIP) += monitor_wip/wip.o
obj-$(CONFIG_RV_MON_WWNR) += monitor_wwnr/wwnr.o
+obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
+obj-$(CONFIG_RV_REACT_PRINTK) += reactor_printk.o
diff --git a/kernel/trace/rv/reactor_printk.c b/kernel/trace/rv/reactor_printk.c
new file mode 100644
index 000000000000..9f9c9bb2d304
--- /dev/null
+++ b/kernel/trace/rv/reactor_printk.c
@@ -0,0 +1,43 @@
+/*
+ * Printk RV reactor:
+ * Prints the exception msg to the kernel message log.
+ *
+ * Copyright (C) 2019-2022 Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+#include <linux/ftrace.h>
+#include <linux/tracepoint.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/rv.h>
+
+static void rv_printk_reaction(char *msg)
+{
+ printk(msg);
+}
+
+struct rv_reactor rv_printk = {
+ .name = "printk",
+ .description = "prints the exception msg to the kernel message log",
+ .react = rv_printk_reaction
+};
+
+int register_react_printk(void)
+{
+ rv_register_reactor(&rv_printk);
+ return 0;
+}
+
+void unregister_react_printk(void)
+{
+ rv_unregister_reactor(&rv_printk);
+}
+
+module_init(register_react_printk);
+module_exit(unregister_react_printk);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Daniel Bristot de Oliveira");
+MODULE_DESCRIPTION("printk rv reactor: printk if an exception is hit");
