On Saturday, 17 February 2024 02:03:15 CST Greg Kroah-Hartman wrote: > On Thu, Feb 15, 2024 at 01:22:01PM -0600, Elizabeth Figura wrote: > > On Thursday, 15 February 2024 01:28:32 CST Greg Kroah-Hartman wrote: > > > On Wed, Feb 14, 2024 at 05:36:38PM -0600, Elizabeth Figura wrote: > > > > This corresponds to the NT syscall NtCreateSemaphore(). > > > > > > > > Semaphores are one of three types of object to be implemented in this driver, > > > > the others being mutexes and events. > > > > > > > > An NT semaphore contains a 32-bit counter, and is signaled and can be acquired > > > > when the counter is nonzero. The counter has a maximum value which is specified > > > > at creation time. The initial value of the semaphore is also specified at > > > > creation time. There are no restrictions on the maximum and initial value. > > > > > > > > Each object is exposed as an file, to which any number of fds may be opened. > > > > When all fds are closed, the object is deleted. > > > > > > > > Signed-off-by: Elizabeth Figura <zfigura@xxxxxxxxxxxxxxx> > > > > --- > > > > .../userspace-api/ioctl/ioctl-number.rst | 2 + > > > > drivers/misc/ntsync.c | 120 ++++++++++++++++++ > > > > include/uapi/linux/ntsync.h | 21 +++ > > > > 3 files changed, 143 insertions(+) > > > > create mode 100644 include/uapi/linux/ntsync.h > > > > > > > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst > > > > index 457e16f06e04..2f5c6994f042 100644 > > > > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst > > > > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst > > > > @@ -173,6 +173,8 @@ Code Seq# Include File Comments > > > > 'M' 00-0F drivers/video/fsl-diu-fb.h conflict! > > > > 'N' 00-1F drivers/usb/scanner.h > > > > 'N' 40-7F drivers/block/nvme.c > > > > +'N' 80-8F uapi/linux/ntsync.h NT synchronization primitives > > > > + <mailto:wine-devel@xxxxxxxxxx> > > > > 'O' 00-06 mtd/ubi-user.h UBI > > > > 'P' all linux/soundcard.h conflict! > > > > 'P' 60-6F sound/sscape_ioctl.h conflict! > > > > diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c > > > > index e4969ef90722..3ad86d98b82d 100644 > > > > --- a/drivers/misc/ntsync.c > > > > +++ b/drivers/misc/ntsync.c > > > > @@ -5,26 +5,146 @@ > > > > * Copyright (C) 2024 Elizabeth Figura > > > > */ > > > > > > > > +#include <linux/anon_inodes.h> > > > > +#include <linux/file.h> > > > > #include <linux/fs.h> > > > > #include <linux/miscdevice.h> > > > > #include <linux/module.h> > > > > +#include <linux/slab.h> > > > > +#include <uapi/linux/ntsync.h> > > > > > > > > #define NTSYNC_NAME "ntsync" > > > > > > > > +enum ntsync_type { > > > > + NTSYNC_TYPE_SEM, > > > > +}; > > > > + > > > > +struct ntsync_obj { > > > > + enum ntsync_type type; > > > > + > > > > + union { > > > > + struct { > > > > + __u32 count; > > > > + __u32 max; > > > > + } sem; > > > > + } u; > > > > + > > > > + struct file *file; > > > > + struct ntsync_device *dev; > > > > +}; > > > > + > > > > +struct ntsync_device { > > > > + struct file *file; > > > > +}; > > > > > > No reference counting is needed for your ntsync_device? Or are you > > > relying on the reference counting of struct file here? > > > > > > You pass around pointers to this structure, and save it off into other > > > structures, how do you know it is "safe" to do so? > > > > Yes, this relies on the reference counting of struct file. The sync > > objects (semaphore etc.) grab a reference when they're created, via > > get_file(), and release it when they're destroyed. This reference is > > taken from within ioctls on the ntsync_device, so the file must be > > valid when we grab a reference. Maybe I'm missing something, though? > > If the reference count is driven by struct file, that's fine, and great, > otherwise you end up with two different reference counts and keeping > them in sync is impossible. > > But as it wasn't obvious, a comment somewhere here would be helpful for > reviewing and figuring out how this all works in 4 years when someone > has to touch it again. Ah, makes sense. I'll add comments to be clearer about the refcounting relationships, thanks. --Zeb
