if flush_scheduled_work() is allegedly overkill, why do drivers use it?

[Robert P. J. Day]

  working my way through work queues and read this in workqueue.h:

/**
 * flush_scheduled_work - ensure that any scheduled work has run to completion.
 *
 * Forces execution of the kernel-global workqueue and blocks until its
 * completion.
 *
 * Think twice before calling this function!  It's very easy to get into
 * trouble if you don't take great care.  Either of the following situations
 * will lead to deadlock:
 *
 *      One of the work items currently on the workqueue needs to acquire
 *      a lock held by your code or its caller.
 *
 *      Your code is running in the context of a work routine.
 *
 * They will be detected by lockdep when they occur, but the first might not
 * occur very often.  It depends on what work items are on the workqueue and
 * what locks they need, which you have no control over.
 *
 * In most situations flushing the entire workqueue is overkill; you merely
 * need to know that a particular work item isn't queued and isn't running.
 * In such cases you should use cancel_delayed_work_sync() or
 * cancel_work_sync() instead.
 */

  and yet, there are quite a few drivers that do just that:

$ grep -rw flush_scheduled_work drivers
drivers/scsi/scsi_scan.c:	flush_scheduled_work();
drivers/scsi/qla2xxx/qla_target.c:		flush_scheduled_work();
drivers/leds/leds-blinkm.c:		flush_scheduled_work();
drivers/acpi/osl.c:	 * which invoke flush_scheduled_work/acpi_os_wait_events_complete
drivers/staging/olpc_dcon/olpc_dcon.c:	flush_scheduled_work();
drivers/staging/rtl8192u/r8192U_core.c://	flush_scheduled_work();
drivers/staging/wlan-ng/prism2usb.c:		flush_scheduled_work();
drivers/staging/iio/light/tsl2563.c:	flush_scheduled_work();
drivers/staging/iio/light/tsl2563.c:	flush_scheduled_work();
drivers/staging/rtl8712/usb_intf.c:	flush_scheduled_work();
drivers/message/fusion/mptscsih.c:	flush_scheduled_work();
drivers/rtc/rtc-dev.c:			flush_scheduled_work();
drivers/rtc/rtc-88pm860x.c:	flush_scheduled_work();
drivers/misc/mei/main.c:	flush_scheduled_work();
drivers/misc/mei/main.c:	flush_scheduled_work();
... snip, even more after this ...

  so what's up with that?  it seems inconsistent to describe that
kernel-wide routine as "overkill" while a number of drivers continue
to use it.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
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