From d21c95c569c462da20d491b75d0a45bd70ddc1bf Mon Sep 17 00:00:00 2001
From: Jonathan Corbet <corbet@lwn.net>
Date: Fri, 16 May 2008 13:40:30 -0600
Subject: [PATCH] Add "no BKL needed" comments to several drivers

This documents the fact that somebody looked at the relevant open()
functions and concluded that, due to their trivial nature, no locking was
needed.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 arch/cris/arch-v10/drivers/eeprom.c          | 2 +-
 arch/cris/arch-v32/drivers/cryptocop.c       | 2 +-
 drivers/char/cs5535_gpio.c                   | 2 ++
 drivers/char/dtlk.c                          | 2 ++
 drivers/char/pc8736x_gpio.c                  | 1 +
 drivers/char/ppdev.c                         | 1 +
 drivers/char/scx200_gpio.c                   | 1 +
 drivers/char/tb0219.c                        | 1 +
 drivers/char/vr41xx_giu.c                    | 2 ++
 drivers/infiniband/core/ucm.c                | 1 +
 drivers/infiniband/hw/ipath/ipath_file_ops.c | 1 +
 drivers/net/ppp_generic.c                    | 1 +
 drivers/scsi/3w-9xxx.c                       | 2 ++
 drivers/scsi/3w-xxxx.c                       | 2 ++
 drivers/scsi/megaraid.c                      | 5 +++--
 drivers/scsi/megaraid/megaraid_sas.c         | 1 +
 16 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/arch/cris/arch-v10/drivers/eeprom.c b/arch/cris/arch-v10/drivers/eeprom.c
index f1cac9dc75b815..40c6fe4c06f4a0 100644
--- a/arch/cris/arch-v10/drivers/eeprom.c
+++ b/arch/cris/arch-v10/drivers/eeprom.c
@@ -375,7 +375,7 @@ int __init eeprom_init(void)
 }
 
 /* Opens the device. */
-
+/* BKL not needed: no global resources accessed */
 static int eeprom_open(struct inode * inode, struct file * file)
 {
 
diff --git a/arch/cris/arch-v32/drivers/cryptocop.c b/arch/cris/arch-v32/drivers/cryptocop.c
index 9fb58202be99b8..c1720428957586 100644
--- a/arch/cris/arch-v32/drivers/cryptocop.c
+++ b/arch/cris/arch-v32/drivers/cryptocop.c
@@ -2302,7 +2302,7 @@ static int cryptocop_job_setup(struct cryptocop_prio_job **pj, struct cryptocop_
 	return 0;
 }
 
-
+/* No BKL needed here - no global resources accessed */
 static int cryptocop_open(struct inode *inode, struct file *filp)
 {
 	int p = iminor(inode);
diff --git a/drivers/char/cs5535_gpio.c b/drivers/char/cs5535_gpio.c
index c0a4a0bb509e77..628e3d3249d216 100644
--- a/drivers/char/cs5535_gpio.c
+++ b/drivers/char/cs5535_gpio.c
@@ -153,6 +153,8 @@ static ssize_t cs5535_gpio_read(struct file *file, char __user *buf,
 	return count;
 }
 
+/* No BKL needed here - "mask" is the only global resource used
+   here and it's a boot-time parameter */
 static int cs5535_gpio_open(struct inode *inode, struct file *file)
 {
 	u32 m = iminor(inode);
diff --git a/drivers/char/dtlk.c b/drivers/char/dtlk.c
index abde6ddefe696e..433388c6023565 100644
--- a/drivers/char/dtlk.c
+++ b/drivers/char/dtlk.c
@@ -288,6 +288,8 @@ static int dtlk_ioctl(struct inode *inode,
 	}
 }
 
+/* No BKL needed here; "dtlk_busy" is the only global resource,
+   and it is not ever set by anybody (test is broken) */
 static int dtlk_open(struct inode *inode, struct file *file)
 {
 	TRACE_TEXT("(dtlk_open");
diff --git a/drivers/char/pc8736x_gpio.c b/drivers/char/pc8736x_gpio.c
index ecfaf180e5bd8b..8715dc9f4a531f 100644
--- a/drivers/char/pc8736x_gpio.c
+++ b/drivers/char/pc8736x_gpio.c
@@ -212,6 +212,7 @@ static struct nsc_gpio_ops pc8736x_gpio_ops = {
 	.gpio_current	= pc8736x_gpio_current
 };
 
+/* No BKL needed here; no global resources accessed */
 static int pc8736x_gpio_open(struct inode *inode, struct file *file)
 {
 	unsigned m = iminor(inode);
diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index 3aab837d9480ae..ce198757488837 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -633,6 +633,7 @@ static int pp_ioctl(struct inode *inode, struct file *file,
 	return 0;
 }
 
+/* No BKL needed here: only local resources used */
 static int pp_open (struct inode * inode, struct file * file)
 {
 	unsigned int minor = iminor(inode);
diff --git a/drivers/char/scx200_gpio.c b/drivers/char/scx200_gpio.c
index 99e5272e3c53e1..be2c623a9862f6 100644
--- a/drivers/char/scx200_gpio.c
+++ b/drivers/char/scx200_gpio.c
@@ -46,6 +46,7 @@ struct nsc_gpio_ops scx200_gpio_ops = {
 };
 EXPORT_SYMBOL_GPL(scx200_gpio_ops);
 
+/* No BKL needed here: no global resources used */
 static int scx200_gpio_open(struct inode *inode, struct file *file)
 {
 	unsigned m = iminor(inode);
diff --git a/drivers/char/tb0219.c b/drivers/char/tb0219.c
index 4c431cb7cf1b1f..db8c2ca2ce4cf2 100644
--- a/drivers/char/tb0219.c
+++ b/drivers/char/tb0219.c
@@ -232,6 +232,7 @@ static ssize_t tanbac_tb0219_write(struct file *file, const char __user *data,
 	return i;
 }
 
+/* No BKL needed here; no global resources accessed */
 static int tanbac_tb0219_open(struct inode *inode, struct file *file)
 {
 	unsigned int minor;
diff --git a/drivers/char/vr41xx_giu.c b/drivers/char/vr41xx_giu.c
index e5ed09192be867..412937fdb958da 100644
--- a/drivers/char/vr41xx_giu.c
+++ b/drivers/char/vr41xx_giu.c
@@ -543,6 +543,8 @@ static ssize_t gpio_write(struct file *file, const char __user *data,
 	return i;
 }
 
+/* No BKL needed here; only global (giu_nr_pins) is only set
+   at probe time */
 static int gpio_open(struct inode *inode, struct file *file)
 {
 	unsigned int pin;
diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c
index d7a6881b571d99..3e6a8ff6d76cbc 100644
--- a/drivers/infiniband/core/ucm.c
+++ b/drivers/infiniband/core/ucm.c
@@ -1155,6 +1155,7 @@ static unsigned int ib_ucm_poll(struct file *filp,
 	return mask;
 }
 
+/* No BKL needed here: no global resources used */
 static int ib_ucm_open(struct inode *inode, struct file *filp)
 {
 	struct ib_ucm_file *file;
diff --git a/drivers/infiniband/hw/ipath/ipath_file_ops.c b/drivers/infiniband/hw/ipath/ipath_file_ops.c
index b472b15637f003..e80cfbd4f3fd2d 100644
--- a/drivers/infiniband/hw/ipath/ipath_file_ops.c
+++ b/drivers/infiniband/hw/ipath/ipath_file_ops.c
@@ -1812,6 +1812,7 @@ static int find_shared_port(struct file *fp,
 	return ret;
 }
 
+/* No BKL needed here */
 static int ipath_open(struct inode *in, struct file *fp)
 {
 	/* The real work is performed later in ipath_assign_port() */
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 1f4ca2b54a7337..dc8505062da725 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -351,6 +351,7 @@ static const int npindex_to_ethertype[NUM_NP] = {
  * Open instances of /dev/ppp can be in one of three states:
  * unattached, attached to a ppp unit, or attached to a ppp channel.
  */
+/* No BKL needed here */
 static int ppp_open(struct inode *inode, struct file *file)
 {
 	/*
diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
index b31faeccb9cde4..2239d16fb9b568 100644
--- a/drivers/scsi/3w-9xxx.c
+++ b/drivers/scsi/3w-9xxx.c
@@ -862,6 +862,8 @@ static int twa_chrdev_ioctl(struct inode *inode, struct file *file, unsigned int
 } /* End twa_chrdev_ioctl() */
 
 /* This function handles open for the character device */
+/* NOTE that this function will race with remove; adding BKL
+   will not help. */
 static int twa_chrdev_open(struct inode *inode, struct file *file)
 {
 	unsigned int minor_number;
diff --git a/drivers/scsi/3w-xxxx.c b/drivers/scsi/3w-xxxx.c
index 8c22329aa85e15..bbff029536ea3d 100644
--- a/drivers/scsi/3w-xxxx.c
+++ b/drivers/scsi/3w-xxxx.c
@@ -1027,6 +1027,8 @@ static int tw_chrdev_ioctl(struct inode *inode, struct file *file, unsigned int
 } /* End tw_chrdev_ioctl() */
 
 /* This function handles open for the character device */
+/* NOTE that this function races with remove - adding BKL
+   won't help */
 static int tw_chrdev_open(struct inode *inode, struct file *file)
 {
 	unsigned int minor_number;
diff --git a/drivers/scsi/megaraid.c b/drivers/scsi/megaraid.c
index 18551aaf5e094e..c9aa2c45a6992d 100644
--- a/drivers/scsi/megaraid.c
+++ b/drivers/scsi/megaraid.c
@@ -3272,8 +3272,9 @@ mega_init_scb(adapter_t *adapter)
  * @filep - unused
  *
  * Routines for the character/ioctl interface to the driver. Find out if this
- * is a valid open. If yes, increment the module use count so that it cannot
- * be unloaded.
+ * is a valid open. 
+ *
+ * No BKL needed here.
  */
 static int
 megadev_open (struct inode *inode, struct file *filep)
diff --git a/drivers/scsi/megaraid/megaraid_sas.c b/drivers/scsi/megaraid/megaraid_sas.c
index 7d84c8bbcf3fc1..81374b7c555ce9 100644
--- a/drivers/scsi/megaraid/megaraid_sas.c
+++ b/drivers/scsi/megaraid/megaraid_sas.c
@@ -2860,6 +2860,7 @@ static void megasas_shutdown(struct pci_dev *pdev)
 
 /**
  * megasas_mgmt_open -	char node "open" entry point
+ * No BKL is needed here.
  */
 static int megasas_mgmt_open(struct inode *inode, struct file *filep)
 {