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Date: Thu, 3 Jun 2021 15:55:34 +0300
From: Adrian Ratiu <adrian.ratiu@...labora.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, kernel@...labora.com,
linux-kernel@...r.kernel.org,
Guillaume Tucker <gtucker.collabora@...il.com>,
Enric Balletbò <enric.balletbo@...labora.com>
Subject: [RFC PATCH 1/1] drivers: base: Expose probe failures via debugfs
This adds a new devices_failed debugfs attribute to list driver
probe failures excepting -EPROBE_DEFER which are still handled
as before via their own devices_deferred attribute.
This is useful on automated test systems like KernelCI to avoid
filtering dmesg dev_err() messages to extract potential probe
failures.
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Guillaume Tucker <gtucker.collabora@...il.com>
Suggested-by: Enric Balletbò <enric.balletbo@...labora.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@...labora.com>
---
drivers/base/core.c | 76 +++++++++++++++++++++++++++++++++++++++++++--
lib/Kconfig.debug | 23 ++++++++++++++
2 files changed, 96 insertions(+), 3 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index b8a8c96dca58..74bf057234b8 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -9,7 +9,9 @@
*/
#include <linux/acpi.h>
+#include <linux/circ_buf.h>
#include <linux/cpufreq.h>
+#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fwnode.h>
@@ -53,6 +55,15 @@ static DEFINE_MUTEX(fwnode_link_lock);
static bool fw_devlink_is_permissive(void);
static bool fw_devlink_drv_reg_done;
+#ifdef CONFIG_DEBUG_FS_PROBE_ERR
+#define PROBE_ERR_BUF_ELEM_SIZE 64
+#define PROBE_ERR_BUF_SIZE (1 << CONFIG_DEBUG_FS_PROBE_ERR_BUF_SHIFT)
+static struct circ_buf probe_err_crbuf;
+static char failed_probe_buffer[PROBE_ERR_BUF_SIZE];
+static DEFINE_MUTEX(failed_probe_mutex);
+static struct dentry *devices_failed_probe;
+#endif
+
/**
* fwnode_link_add - Create a link between two fwnode_handles.
* @con: Consumer end of the link.
@@ -3769,6 +3780,29 @@ struct device *device_find_child_by_name(struct device *parent,
}
EXPORT_SYMBOL_GPL(device_find_child_by_name);
+/*
+ * failed_devs_show() - Show devices & drivers which failed to probe.
+ */
+#ifdef CONFIG_DEBUG_FS_PROBE_ERR
+static int failed_devs_show(struct seq_file *s, void *data)
+{
+ size_t offset;
+
+ mutex_lock(&failed_probe_mutex);
+
+ for (offset = 0;
+ offset < PROBE_ERR_BUF_SIZE;
+ offset += PROBE_ERR_BUF_ELEM_SIZE)
+ if (probe_err_crbuf.buf[offset])
+ seq_printf(s, "%s\n", probe_err_crbuf.buf + offset);
+
+ mutex_unlock(&failed_probe_mutex);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(failed_devs);
+#endif
+
int __init devices_init(void)
{
devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
@@ -3784,6 +3818,12 @@ int __init devices_init(void)
if (!sysfs_dev_char_kobj)
goto char_kobj_err;
+#ifdef CONFIG_DEBUG_FS_PROBE_ERR
+ devices_failed_probe = debugfs_create_file("devices_failed", 0444, NULL,
+ NULL, &failed_devs_fops);
+ probe_err_crbuf.buf = failed_probe_buffer;
+#endif
+
return 0;
char_kobj_err:
@@ -4623,6 +4663,34 @@ define_dev_printk_level(_dev_info, KERN_INFO);
#endif
+/**
+ * device_log_probe_failure: Print err to kernel log then add debugfs entry
+ * @dev: the pointer to the struct device
+ * @err: error value to print
+ * @vaf: struct containing printf-style error format string and arguments
+ */
+void device_log_probe_failure(const struct device *dev, int err,
+ struct va_format *vaf)
+{
+ dev_err(dev, "error %pe: %pV", ERR_PTR(err), vaf);
+
+#ifdef CONFIG_DEBUG_FS_PROBE_ERR
+ mutex_lock(&failed_probe_mutex);
+
+ snprintf(probe_err_crbuf.buf + probe_err_crbuf.head,
+ PROBE_ERR_BUF_ELEM_SIZE,
+ "%s %s %d %pV",
+ dev_driver_string(dev), dev_name(dev), err, vaf);
+
+ if (probe_err_crbuf.head < PROBE_ERR_BUF_SIZE - PROBE_ERR_BUF_ELEM_SIZE)
+ probe_err_crbuf.head += PROBE_ERR_BUF_ELEM_SIZE;
+ else
+ probe_err_crbuf.head = 0;
+
+ mutex_unlock(&failed_probe_mutex);
+#endif
+}
+
/**
* dev_err_probe - probe error check and log helper
* @dev: the pointer to the struct device
@@ -4631,10 +4699,12 @@ define_dev_printk_level(_dev_info, KERN_INFO);
* @...: arguments as specified in the format string
*
* This helper implements common pattern present in probe functions for error
- * checking: print debug or error message depending if the error value is
- * -EPROBE_DEFER and propagate error upwards.
+ * checking: print debug or error message depending on the error value and then
+ * propagate the error upwards.
* In case of -EPROBE_DEFER it sets also defer probe reason, which can be
* checked later by reading devices_deferred debugfs attribute.
+ * Errors other than -EPROBE_DEFER can be checked by reading the devices_failed
+ * debugfs attribute if CONFIG_DEBUG_FS_PROBE_ERR is enabled.
* It replaces code sequence::
*
* if (err != -EPROBE_DEFER)
@@ -4660,7 +4730,7 @@ int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
vaf.va = &args;
if (err != -EPROBE_DEFER) {
- dev_err(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+ device_log_probe_failure(dev, err, &vaf);
} else {
device_set_deferred_probe_reason(dev, &vaf);
dev_dbg(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 150f13baa6cc..10044ba47c26 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -578,6 +578,29 @@ config DEBUG_FS_ALLOW_NONE
endchoice
+config DEBUG_FS_PROBE_ERR
+ bool "Show device driver probe failures"
+ depends on DEBUG_FS
+ help
+ This feature enables a devices_failed debugfs attribute exposing
+ driver probe failures different from -EPROBE_DEFER.
+
+config DEBUG_FS_PROBE_ERR_BUF_SHIFT
+ int "Probe failures log buffer size"
+ depends on DEBUG_FS && DEBUG_FS_PROBE_ERR
+ range 12 16
+ default 12
+ help
+ This options allows to increase the default ringbuffer size for
+ driver probe failures as a power of 2.
+
+ Examples:
+ 16 => 64 KB
+ 15 => 32 KB
+ 14 => 16 KB
+ 13 => 8 KB
+ 12 => 4 KB
+
source "lib/Kconfig.kgdb"
source "lib/Kconfig.ubsan"
source "lib/Kconfig.kcsan"
--
2.31.1
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