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Verified Commit 6d8a1e34 authored by John Dias's avatar John Dias Committed by Manu Suresh
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fs: Improve eventpoll logging to stop indicting timerfd 



timerfd doesn't create any wakelocks; eventpoll can, and is creating the
wakelocks we see called "[timerfd]".  eventpoll creates two kinds of
wakelocks: a single top-level lock associated with the eventpoll fd
itself, and one additional lock for each fd it is polling that needs such
a lock (e.g. those using EPOLLWAKEUP).  Current code names the per-fd
locks using the undecorated names of the fds' associated files (hence
"[timerfd]"), and is naming the top-level lock after the PID of the caller
and the name of the file behind the first fd for which a per-fd lock is
created.  To make things clearer, the top-level lock is now named using
the caller PID and an "epollfd" designation, while the per-fd locks are
also named with the caller's PID (to associate them with the top-level
lock) and their respective fds' file names.

Port of fix already applied to previous 2 generations.  Note that this
set of changes does not fully solve the problem of eventpoll/timerfd
wakelock attribution to the original process, since most activity is
relayed through system_server, but it does at least ensure that different
eventpoll wakelocks - and their stats - are properly disambiguated.

Test: Ran on device and observed new wakelock naming in
/d/wakeup_sources and (file naming in) lsof output.
Bug: 146917063
Bug: 116363986
Change-Id: I34bada5ddab04cf3830762c745f46bfcd1549cb8
Signed-off-by: default avatarJohn Dias <joaodias@google.com>
Signed-off-by: default avatarKelly Rossmoyer <krossmo@google.com>
Signed-off-by: default avatarMiguel de Dios <migueldedios@google.com>
(cherry picked from commit 3c482c62a7b71c0f971067ff09e9ef9abf5b7a0b)
(Manu: update for 5.4)
parent e7efc807

fs/eventpoll.c

+10 −2
Original line number Diff line number Diff line
@@ -1456,15 +1456,23 @@ static int ep_create_wakeup_source(struct epitem *epi) 
{

	struct name_snapshot n;

	struct wakeup_source *ws;

	char task_comm_buf[TASK_COMM_LEN];

	char buf[64];



	get_task_comm(task_comm_buf, current);



	if (!epi->ep->ws) {

		epi->ep->ws = wakeup_source_register(NULL, "eventpoll");

		snprintf(buf, sizeof(buf), "epoll_%.*s_epollfd",

			 (int)sizeof(task_comm_buf), task_comm_buf);

		epi->ep->ws = wakeup_source_register(NULL, buf);

		if (!epi->ep->ws)

			return -ENOMEM;

	}



	take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);

	ws = wakeup_source_register(NULL, n.name.name);

	snprintf(buf, sizeof(buf), "epoll_%.*s_file:%s",

		(int)sizeof(task_comm_buf), task_comm_buf, n.name.name);

	ws = wakeup_source_register(NULL, buf);

	release_dentry_name_snapshot(&n);



	if (!ws)

fs/timerfd.c

+11 −1
Original line number Diff line number Diff line
@@ -45,6 +45,8 @@ struct timerfd_ctx { 
	bool might_cancel;

};



static atomic_t instance_count = ATOMIC_INIT(0);



static LIST_HEAD(cancel_list);

static DEFINE_SPINLOCK(cancel_lock);
@@ -388,6 +390,9 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags) 
{

	int ufd;

	struct timerfd_ctx *ctx;

	char task_comm_buf[TASK_COMM_LEN];

	char file_name_buf[32];

	int instance;



	/* Check the TFD_* constants for consistency.  */

	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
@@ -424,7 +429,12 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags) 


	ctx->moffs = ktime_mono_to_real(0);



	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,

	instance = atomic_inc_return(&instance_count);

	get_task_comm(task_comm_buf, current);

	snprintf(file_name_buf, sizeof(file_name_buf), "[timerfd%d_%.*s]",

		 instance, (int)sizeof(task_comm_buf), task_comm_buf);



	ufd = anon_inode_getfd(file_name_buf, &timerfd_fops, ctx,

			       O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));

	if (ufd < 0)

		kfree(ctx);