diff mbox series

[v4] fs: Improve eventpoll logging to stop indicting timerfd

Message ID 20240604173606.998721-1-isaacmanjarres@google.com (mailing list archive)
State New
Headers show
Series [v4] fs: Improve eventpoll logging to stop indicting timerfd | expand

Commit Message

Isaac Manjarres June 4, 2024, 5:36 p.m. UTC
From: Manish Varma <varmam@google.com>

timerfd doesn't create any wakelocks, but eventpoll can.  When it does,
it names them after the underlying file descriptor, and since all
timerfd file descriptors are named "[timerfd]" (which saves memory on
systems like desktops with potentially many timerfd instances), all
wakesources created as a result of using the eventpoll-on-timerfd idiom
are called... "[timerfd]".

However, it becomes impossible to tell which "[timerfd]" wakesource is
affliated with which process and hence troubleshooting is difficult.

This change addresses this problem by changing the way eventpoll
wakesources are named:

1) the top-level per-process eventpoll wakesource is now named
"epollN:P" (instead of just "eventpoll"), where N is a unique ID token,
and P is the PID of the creating process.
2) individual per-underlying-file descriptor eventpoll wakesources are
now named "epollitemN:P.F", where N is a unique ID token and P is PID
of the creating process and F is the name of the underlying file
descriptor.

Co-developed-by: Kelly Rossmoyer <krossmo@google.com>
Signed-off-by: Kelly Rossmoyer <krossmo@google.com>
Signed-off-by: Manish Varma <varmam@google.com>
Co-developed-by: Isaac J. Manjarres <isaacmanjarres@google.com>
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
---
 drivers/base/power/wakeup.c | 10 ++++++++--
 fs/eventpoll.c              | 11 +++++++++--
 include/linux/pm_wakeup.h   |  4 ++--
 3 files changed, 19 insertions(+), 6 deletions(-)

 v1 -> v2:
 - Renamed instance count to wakesource_create_id to better describe
   its purpose.
 - Changed the wakeup source naming convention for wakeup sources
   created by eventpoll to avoid changing the timerfd names.
 - Used the PID of the process instead of the process name for the
   sake of uniqueness when creating wakeup sources.

v2 -> v3:
 - Changed wakeup_source_register() to take in a format string
   and arguments to avoid duplicating code to construct wakeup
   source names.
 - Moved the definition of wakesource_create_id so that it is
   always defined to fix an compilation error.

v3 -> v4:
 - Changed the naming convention for the top-level epoll wakeup
   sources to include an ID for uniqueness. This is needed in
   cases where a process is using two epoll fds.
 - Edited commit log to reflect new changes and add new tags.

Comments

kernel test robot June 4, 2024, 10:13 p.m. UTC | #1
Hi Isaac,

kernel test robot noticed the following build warnings:

[auto build test WARNING on rafael-pm/linux-next]
[also build test WARNING on rafael-pm/bleeding-edge linus/master v6.10-rc2 next-20240604]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Isaac-J-Manjarres/fs-Improve-eventpoll-logging-to-stop-indicting-timerfd/20240605-013918
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
patch link:    https://lore.kernel.org/r/20240604173606.998721-1-isaacmanjarres%40google.com
patch subject: [PATCH v4] fs: Improve eventpoll logging to stop indicting timerfd
config: um-i386_defconfig (https://download.01.org/0day-ci/archive/20240605/202406050504.UvdlPAQ0-lkp@intel.com/config)
compiler: gcc-13 (Ubuntu 13.2.0-4ubuntu3) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240605/202406050504.UvdlPAQ0-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406050504.UvdlPAQ0-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/base/power/wakeup.c: In function 'wakeup_source_register':
>> drivers/base/power/wakeup.c:223:9: warning: function 'wakeup_source_register' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
     223 |         vsnprintf(name, sizeof(name), fmt, args);
         |         ^~~~~~~~~


vim +223 drivers/base/power/wakeup.c

   208	
   209	/**
   210	 * wakeup_source_register - Create wakeup source and add it to the list.
   211	 * @dev: Device this wakeup source is associated with (or NULL if virtual).
   212	 * @fmt: format string for the wakeup source name
   213	 */
   214	struct wakeup_source *wakeup_source_register(struct device *dev,
   215						     const char *fmt, ...)
   216	{
   217		struct wakeup_source *ws;
   218		int ret;
   219		char name[128];
   220		va_list args;
   221	
   222		va_start(args, fmt);
 > 223		vsnprintf(name, sizeof(name), fmt, args);
   224		va_end(args);
   225	
   226		ws = wakeup_source_create(name);
   227		if (ws) {
   228			if (!dev || device_is_registered(dev)) {
   229				ret = wakeup_source_sysfs_add(dev, ws);
   230				if (ret) {
   231					wakeup_source_free(ws);
   232					return NULL;
   233				}
   234			}
   235			wakeup_source_add(ws);
   236		}
   237		return ws;
   238	}
   239	EXPORT_SYMBOL_GPL(wakeup_source_register);
   240
diff mbox series

Patch

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 752b417e8129..86276f904be8 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -209,13 +209,19 @@  EXPORT_SYMBOL_GPL(wakeup_source_remove);
 /**
  * wakeup_source_register - Create wakeup source and add it to the list.
  * @dev: Device this wakeup source is associated with (or NULL if virtual).
- * @name: Name of the wakeup source to register.
+ * @fmt: format string for the wakeup source name
  */
 struct wakeup_source *wakeup_source_register(struct device *dev,
-					     const char *name)
+					     const char *fmt, ...)
 {
 	struct wakeup_source *ws;
 	int ret;
+	char name[128];
+	va_list args;
+
+	va_start(args, fmt);
+	vsnprintf(name, sizeof(name), fmt, args);
+	va_end(args);
 
 	ws = wakeup_source_create(name);
 	if (ws) {
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f53ca4f7fced..941df15208a4 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -338,6 +338,7 @@  static void __init epoll_sysctls_init(void)
 #define epoll_sysctls_init() do { } while (0)
 #endif /* CONFIG_SYSCTL */
 
+static atomic_t wakesource_create_id  = ATOMIC_INIT(0);
 static const struct file_operations eventpoll_fops;
 
 static inline int is_file_epoll(struct file *f)
@@ -1545,15 +1546,21 @@  static int ep_create_wakeup_source(struct epitem *epi)
 {
 	struct name_snapshot n;
 	struct wakeup_source *ws;
+	pid_t task_pid;
+	int id;
+
+	task_pid = task_pid_nr(current);
 
 	if (!epi->ep->ws) {
-		epi->ep->ws = wakeup_source_register(NULL, "eventpoll");
+		id = atomic_inc_return(&wakesource_create_id);
+		epi->ep->ws = wakeup_source_register(NULL, "epoll:%d:%d", id, task_pid);
 		if (!epi->ep->ws)
 			return -ENOMEM;
 	}
 
+	id = atomic_inc_return(&wakesource_create_id);
 	take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);
-	ws = wakeup_source_register(NULL, n.name.name);
+	ws = wakeup_source_register(NULL, "epollitem%d:%d.%s", id, task_pid, n.name.name);
 	release_dentry_name_snapshot(&n);
 
 	if (!ws)
diff --git a/include/linux/pm_wakeup.h b/include/linux/pm_wakeup.h
index 76cd1f9f1365..40972ca262cc 100644
--- a/include/linux/pm_wakeup.h
+++ b/include/linux/pm_wakeup.h
@@ -100,7 +100,7 @@  extern void wakeup_source_destroy(struct wakeup_source *ws);
 extern void wakeup_source_add(struct wakeup_source *ws);
 extern void wakeup_source_remove(struct wakeup_source *ws);
 extern struct wakeup_source *wakeup_source_register(struct device *dev,
-						    const char *name);
+						    const char *fmt, ...);
 extern void wakeup_source_unregister(struct wakeup_source *ws);
 extern int wakeup_sources_read_lock(void);
 extern void wakeup_sources_read_unlock(int idx);
@@ -141,7 +141,7 @@  static inline void wakeup_source_add(struct wakeup_source *ws) {}
 static inline void wakeup_source_remove(struct wakeup_source *ws) {}
 
 static inline struct wakeup_source *wakeup_source_register(struct device *dev,
-							   const char *name)
+							   const char *fmt, ...)
 {
 	return NULL;
 }