On Fri, Oct 25, 2024 at 6:41 PM John Hubbard jhubbard@nvidia.com wrote:
On 10/25/24 5:50 AM, Pedro Falcato wrote:
On Fri, Oct 25, 2024 at 10:41 AM Lorenzo Stoakes lorenzo.stoakes@oracle.com wrote:
...
+static inline int pidfd_is_self_sentinel(pid_t pid) +{
return pid == PIDFD_SELF_THREAD || pid == PIDFD_SELF_THREAD_GROUP;+}
Do we want this in the uapi header? Even if this is useful, it might come with several drawbacks such as breaking scripts that parse kernel headers (and a quick git grep suggests we do have static inlines in headers, but in rather obscure ones) and breaking C89:
Let's please not say "C89" anymore, we've moved on! :)
The notes in [1], which is now nearly 2.5 years old, discuss the move to C11, and specifically how to handle the inline keyword.
That seems to only apply to the kernel internally, uapi headers are included from userspace too (-std=c89 -pedantic doesn't know what a gnu extension is). And uapi headers _generally_ keep to defining constants and structs, nothing more. I don't know what the guidelines for uapi headers are nowadays, but we generally want to not break userspace.
I think it's quite clear at this point, that we should not hold up new work, based on concerns about handling the inline keyword, nor about C89.
Right, but the correct solution is probably to move pidfd_is_self_sentinel to some other place, since it's not even supposed to be used by userspace (it's semantically useless to userspace, and it's only two users are in the kernel, kernel/pid.c and exit.c).