Make all it87 drivers SMP safe.

There are 3 different drivers that touch the it87 hardware registers. The 3 drivers have been written independently and access the it87 hardware registers assuming they are the only driver accessing it. This change attempts to serialize access to the hardware by defining a global spinlock it87_io_lock in a file it87_lock.c. This lock has to be acquired by each of the it87 drivers before it can access the hardware. We have defined a new Kconfig option IT87_LOCK. When it is selected it87_lock.c is compiled into the kernel thereby making the lock global and accessable to the it87 drivers which are typically built as loadable modules. All the it87 drivers select IT87_LOCK to compile the lock into the kernel.
The routines accessing the hardware are being called from module init, open, ioctl and module exit routines and hence it is sufficient to use calls to spin_lock and spin_unlock to acquire and release the locks. For the same reasons it87_wdt.c has extensive changes to remove calls to spin_lock_irqsave and spin_unlock_irqrestore. The lock is now acquired in superio_enter and released in superio_exit. This is now identical to the code in drivers/hwmon/it87.c and drivers/watchdog/it8712f_wdt.c. Added __acquire and __release annotations wherever needed.

01 - Adds the relevant lock files.
drivers/watchdog/Kconfig
drivers/watchdog/Makefile
drivers/watchdog/it87_lock.c
include/linux/it87_lock.h

02 - Adds changes to watchdog drivers to use the new lock.
drivers/watchdog/it8712f_wdt.c drivers/watchdog/it87_wdt.c

03 - Adds changes to hwmon driver to use the new lock.
drivers/hwmon/Kconfig
drivers/hwmon/it87.c

 drivers/hwmon/Kconfig          |    1 +
 drivers/hwmon/it87.c           |   14 ++++++++++++-
 drivers/watchdog/Kconfig       |   12 +++++++++++
 drivers/watchdog/Makefile      |    1 +
 drivers/watchdog/it8712f_wdt.c |   10 ++++----
 drivers/watchdog/it87_lock.c   |   27 +++++++++++++++++++++++++
 drivers/watchdog/it87_wdt.c    |   42 ++++++---------------------------------
 include/linux/it87_lock.h      |   28 ++++++++++++++++++++++++++
 8 files changed, 96 insertions(+), 41 deletions(-)
 create mode 100644 drivers/watchdog/it87_lock.c
 create mode 100644 include/linux/it87_lock.h

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Did you consider naming this file include/linux/it87.h as suggested ? I thought that was a goodd idea.

When you send out new versions of your patch set, it would be prudent to list the patch version, as well as the changes made compared to previous versions of your patch. See Documents/SubmittingPatches, rule #2.

Thanks,
Guenter

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Guenter,
Comments are below

This does seem to be a good idea. I had some other thoughts about where to place the
it87_lock.c file. One thought was to move the lock into the drivers/mfd directory and
completely decouple the lock from the watchdog or the hwmon directories. The mfd/Kconfig
would contain the IT87_LOCK.

I am new at this. Exactly where do you list the patch version. I put v2 in the subject line.
The only difference between the 2 patch sets was that each of the patches has a more verbose body section explaining the contents of the patch and each of the sub patch
Subject line reflected what was happening in that sub patch. I also made sure I had the
"In-Reply-To" entry in the patches.

Where in the patch do you discuss the changes made with respect to the previous patch.

When I send out the next set of patches do I have to send out the entire patch set marked as v3.

--
Regards
Nat Gurumoorthy AB6SJ

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Might make sense, but I would suggest to solicit feedback from others before you do that. Specifically you'll need some guidance from the watchdog maintainer and possibly from the mfd maintainer if your current solution is acceptable or if the mfd solution would be better (ie more likely to be accepted).

If you move the lock handling to mfd, you probably want to name the file it87.c, or maybe it87-core.c, to ensure that other functionality can be added to it without having to rename the file.

That was ok.

This somehow didn't work. If you look at the kernel.org mailing list, it did not recognize your series of patches as a single thread, but lists it as independent posts.

You might want to play with that by sending series of patches to yourself and check if your mailer recognizes it as one thread.

See SubmittingPatches, #15. Add version information (ie what changed in which version) after the "---" marker line, such as

---
v2: Changed subject line to be meaningful, added description

One hint - the first comment line in each of your patches is a bit odd and should not really be there. Keep in mind that everything up to the "---" line will end up in the commit log unless the maintainer takes it out. The rest of the explanations looked ok to me.

If you change the header file name and/or location, each of the patches will be affected, so each of the patches should get a new version number. If you don't change anything, don't resubmit (yet).

Thanks,
Guenter

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