On Fri, Oct 30, 2020 at 06:30:49PM +1100, Anand K. Mistry wrote: > On Fri, 30 Oct 2020 at 18:20, Greg Kroah-Hartman > <gre...@linuxfoundation.org> wrote: > > > > On Fri, Oct 30, 2020 at 06:04:42PM +1100, Anand K Mistry wrote: > > > This mirrors support for exporting atomic_t values. > > > > > > Signed-off-by: Anand K Mistry <amis...@google.com> > > > > > > --- > > > > > > fs/debugfs/file.c | 37 +++++++++++++++++++++++++++++++++++++ > > > include/linux/debugfs.h | 6 ++++++ > > > 2 files changed, 43 insertions(+) > > > > > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c > > > index a768a09430c3..798bd3bdedec 100644 > > > --- a/fs/debugfs/file.c > > > +++ b/fs/debugfs/file.c > > > @@ -770,6 +770,43 @@ void debugfs_create_atomic_t(const char *name, > > > umode_t mode, > > > } > > > EXPORT_SYMBOL_GPL(debugfs_create_atomic_t); > > > > > > +static int debugfs_atomic64_t_set(void *data, u64 val) > > > +{ > > > + atomic64_set((atomic64_t *)data, val); > > > + return 0; > > > +} > > > +static int debugfs_atomic64_t_get(void *data, u64 *val) > > > +{ > > > + *val = atomic64_read((atomic64_t *)data); > > > + return 0; > > > +} > > > +DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic64_t, debugfs_atomic64_t_get, > > > + debugfs_atomic64_t_set, "%lld\n"); > > > +DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic64_t_ro, debugfs_atomic64_t_get, > > > NULL, > > > + "%lld\n"); > > > +DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic64_t_wo, NULL, > > > debugfs_atomic64_t_set, > > > + "%lld\n"); > > > + > > > +/** > > > + * debugfs_create_atomic64_t - create a debugfs file that is used to > > > read and > > > + * write an atomic64_t value > > > + * @name: a pointer to a string containing the name of the file to > > > create. > > > + * @mode: the permission that the file should have > > > + * @parent: a pointer to the parent dentry for this file. This should > > > be a > > > + * directory dentry if set. If this parameter is %NULL, then > > > the > > > + * file will be created in the root of the debugfs filesystem. > > > + * @value: a pointer to the variable that the file should read to and > > > write > > > + * from. > > > + */ > > > +void debugfs_create_atomic64_t(const char *name, umode_t mode, > > > + struct dentry *parent, atomic64_t *value) > > > +{ > > > + debugfs_create_mode_unsafe(name, mode, parent, value, > > > + &fops_atomic64_t, &fops_atomic64_t_ro, > > > + &fops_atomic64_t_wo); > > > +} > > > +EXPORT_SYMBOL_GPL(debugfs_create_atomic64_t); > > > + > > > ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf, > > > size_t count, loff_t *ppos) > > > { > > > diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h > > > index 851dd1f9a8a5..0fac84c53eab 100644 > > > --- a/include/linux/debugfs.h > > > +++ b/include/linux/debugfs.h > > > @@ -126,6 +126,8 @@ void debugfs_create_size_t(const char *name, umode_t > > > mode, > > > struct dentry *parent, size_t *value); > > > void debugfs_create_atomic_t(const char *name, umode_t mode, > > > struct dentry *parent, atomic_t *value); > > > +void debugfs_create_atomic64_t(const char *name, umode_t mode, > > > + struct dentry *parent, atomic64_t > > > *value); > > > struct dentry *debugfs_create_bool(const char *name, umode_t mode, > > > struct dentry *parent, bool *value); > > > > > > @@ -291,6 +293,10 @@ static inline void debugfs_create_atomic_t(const > > > char *name, umode_t mode, > > > atomic_t *value) > > > { } > > > > > > +static inline void debugfs_create_atomic64_t(const char *name, umode_t > > > mode, > > > + struct dentry *parent, > > > atomic64_t *value) > > > +{ } > > > + > > > static inline struct dentry *debugfs_create_bool(const char *name, > > > umode_t mode, > > > struct dentry *parent, > > > bool *value) > > > > Looks good, but where is the user of this code? I can't add new apis > > without a user. > > Fair enough. Right now, the user is just some local > debugging/performance measuring which will never be upstreamed. > Happy to let this drop.
Now dropped! > > And are you _SURE_ you want to be using an atomic64_t in the first > > place? We are starting to reduce the "raw" usage of atomic variables as > > almost no one needs them, they should be using something else instead, > > or just a u64 as atomics are not needed for simple statistics. > > I understand, and would generally never use atomics in real code. I > used an atomic since I wanted accuracy (for some of the benchmarks I > want to run) but can't use anything that blocks (spinlock/mutex) since > the code is somewhere inside the scheduler. You can't be "accurate" for a single value from a single file read by userspace as you don't know if it changed right after you read the value :) Again, people abuse atomic values thinking they are something they really aren't... thanks, greg k-h