On Fri, Jul 26, 2024 at 2:49 PM Matt Bobrowski <mattbobrowski@xxxxxxxxxx> wrote: > > On Fri, Jul 26, 2024 at 02:25:26PM -0700, Song Liu wrote: > > On Fri, Jul 26, 2024 at 1:56 AM Matt Bobrowski <mattbobrowski@xxxxxxxxxx> wrote: > > > > > [...] > > > + len = buf + buf__sz - ret; > > > + memmove(buf, ret, len); > > > + return len; > > > +} > > > +__bpf_kfunc_end_defs(); > > > + > > > +BTF_KFUNCS_START(bpf_fs_kfunc_set_ids) > > > +BTF_ID_FLAGS(func, bpf_get_task_exe_file, > > > + KF_ACQUIRE | KF_TRUSTED_ARGS | KF_SLEEPABLE | KF_RET_NULL) > > > +BTF_ID_FLAGS(func, bpf_put_file, KF_RELEASE | KF_SLEEPABLE) > > > > Do we really need KF_SLEEPABLE for bpf_put_file? > > Well, the guts of fput() is annotated w/ might_sleep(), so the calling > thread may presumably be involuntarily put to sleep? You can also see > the guts of fput() invoking various indirect function calls > i.e. ->release(), and depending on the implementation of those, they > could be initiating resource release related actions which > consequently could result in waiting for some I/O to be done? fput() > also calls dput() and mntput() and these too can also do a bunch of > teardown. > > Please correct me if I've misunderstood something. __fput() is annotated with might_sleep(). However, fput() doesn't not call __fput() directly. Instead, it schedules a worker to call __fput(). Therefore, it is safe to call fput() from a non-sleepable context. Thanks, Song
