WorkStruct: Pass the work_struct pointer instead of context data

Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.

For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.

To make this work, an extra flag is introduced into the management side of the
work_struct.  This governs auto-release of the structure upon execution.

Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function.  This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated..  This is a
problem if the auxiliary data is taken away (as done by the last patch).

However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems.  But then the work function must itself release the
work_struct by calling work_release().

In most cases, automatic release is fine, so this is the default.  Special
initiators exist for the non-auto-release case (ending in _NAR).


Signed-Off-By: David Howells <dhowells@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 8e4413f6fbaf..8ee04adc37f0 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -155,7 +155,7 @@ static void con_flush_chars(struct tty_struct *tty);
 static void set_vesa_blanking(char __user *p);
 static void set_cursor(struct vc_data *vc);
 static void hide_cursor(struct vc_data *vc);
-static void console_callback(void *ignored);
+static void console_callback(struct work_struct *ignored);
 static void blank_screen_t(unsigned long dummy);
 static void set_palette(struct vc_data *vc);
 
@@ -174,7 +174,7 @@ static int vesa_blank_mode; /* 0:none 1:suspendV 2:suspendH 3:powerdown */
 static int blankinterval = 10*60*HZ;
 static int vesa_off_interval;
 
-static DECLARE_WORK(console_work, console_callback, NULL);
+static DECLARE_WORK(console_work, console_callback);
 
 /*
  * fg_console is the current virtual console,
@@ -2154,7 +2154,7 @@ out:
  * with other console code and prevention of re-entrancy is
  * ensured with console_sem.
  */
-static void console_callback(void *ignored)
+static void console_callback(struct work_struct *ignored)
 {
         acquire_console_sem();