Add ABI documentation for files in /sys/kernel/error_report/
Requested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
.../ABI/testing/sysfs-kernel-error_report | 41 +++++++++++++++++++
1 file changed, 41 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-error_report
diff --git a/Documentation/ABI/testing/sysfs-kernel-error_report b/Documentation/ABI/testing/sysfs-kernel-error_report
new file mode 100644
index 000000000000..666d039f93a9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-error_report
@@ -0,0 +1,41 @@
+What: /sys/kernel/error_report/
+Date: January 2021
+Contact: Alexander Potapenko <glider@xxxxxxxxxx>,
+ Marco Elver <elver@xxxxxxxxxx>
+Description:
+ /sys/kernel/error_report/ contains two files: "report_count"
+ and "last_report". These files are used to notify userspace
+ about error reports from the enrolled kernel subsystems (those
+ that use error_report_start/error_report_end tracepoints).
+
+ "report_count" contains the current number of reported errors.
+ This number is incremented every time the error_report_end
+ trace event occurs in the kernel.
+
+ "last_report" contains the most recent error report; concurrent
+ report generation results in collection of any one report
+ ("last_report" may not be the last shown on the console).
+ A "report" is everything the task had printed to the console
+ between issuing the error_report_start and error_report_end
+ trace events.
+
+ Due to sysfs limitations, the report size is truncated at
+ PAGE_SIZE. To save space, the leading info in square brackets
+ printed by CONFIG_PRINTK_TIME and CONFIG_PRINTK_CALLER is
+ trimmed from the output lines.
+
+ Both files use sysfs_notify() to notify userspace about
+ changes. Userspace programs can use poll() to block until an
+ error is reported:
+
+ pfd.fd = fd;
+ pfd.events = POLLPRI;
+ while (1) {
+ lseek(pfd.fd, 0, SEEK_SET);
+ poll(&pfd, 1, -1);
+ read(pfd.fd, buffer, PAGE_SIZE);
+ /* Process the report in @buffer. */
+ }
+
+ Files in /sys/kernel/error_report/ are available when
+ CONFIG_ERROR_REPORT_NOTIFY is enabled.
--
2.30.0.284.gd98b1dd5eaa7-goog
