following up on my earlier post, i'm summarizing the current use of
semaphores in the kernel and quite a lot of docs are going to have to
cleanse themselves of now-obsolete references to all of
DECLARE_MUTEX[_LOCKED] and init_MUTEX[_LOCKED], since the current API
consists simply of:
* DEFINE_SEMAPHORE()
* sema_init()
but a quick grep for the former produces only:
$ grep -rw DEFINE_SEMAPHORE *
drivers/macintosh/adb.c:static DEFINE_SEMAPHORE(adb_probe_mutex);
drivers/staging/comedi/drivers/usbduxfast.c:static DEFINE_SEMAPHORE(start_stop_sem);
drivers/staging/comedi/drivers/usbduxsigma.c:static DEFINE_SEMAPHORE(start_stop_sem);
drivers/staging/comedi/drivers/dt9812.c:static DEFINE_SEMAPHORE(dt9812_mutex);
drivers/staging/comedi/drivers/usbdux.c:static DEFINE_SEMAPHORE(start_stop_sem);
drivers/staging/csr/drv.c:DEFINE_SEMAPHORE(udi_mutex);
drivers/staging/csr/io.c:DEFINE_SEMAPHORE(Unifi_instance_mutex);
drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c:static DEFINE_SEMAPHORE(bnx2x_prev_sem);
include/linux/semaphore.h:#define DEFINE_SEMAPHORE(name) \
kernel/printk.c:static DEFINE_SEMAPHORE(console_sem);
$
ignoring what's under drivers/staging/ (which is generally a bit of
a mess at the best of times), the above shows that there is almost
*no* usage of DEFINE_SEMAPHORE(), which surprised me somewhat, but i
can imagine a couple reasons.
first, a lot of semaphores have been replaced by the newer and
simpler mutex. also, rather than semaphores being created standalone,
they're normally defined as part of a structure, and when an instance
of that structure is declared, it's naturally initialized with
sema_init() in the appropriate initialization code.
so i'm not surprised that the usage of DEFINE_SEMAPHORE() is
dropping, i'm just surprised that it's almost non-existent. thoughts?
rday
--
========================================================================
Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca
Twitter: http://twitter.com/rpjday
LinkedIn: http://ca.linkedin.com/in/rpjday
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