From 9be1f8739c176db3bc64f1d5aceec21d512dfc82 Mon Sep 17 00:00:00 2001 From: Kir Kolyshkin Date: Mon, 7 Aug 2023 20:03:57 -0700 Subject: [PATCH] sched/headers: Move 'struct sched_param' out of uapi, to work around glibc/musl breakage MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Both glibc and musl define 'struct sched_param' in sched.h, while kernel has it in uapi/linux/sched/types.h, making it cumbersome to use sched_getattr(2) or sched_setattr(2) from userspace. For example, something like this: #include #include struct sched_attr sa; will result in "error: redefinition of ‘struct sched_param’" (note the code doesn't need sched_param at all -- it needs struct sched_attr plus some stuff from sched.h). The situation is, glibc is not going to provide a wrapper for sched_{get,set}attr, thus the need to include linux/sched_types.h directly, which leads to the above problem. Thus, the userspace is left with a few sub-par choices when it wants to use e.g. sched_setattr(2), such as maintaining a copy of struct sched_attr definition, or using some other ugly tricks. OTOH, 'struct sched_param' is well known, defined in POSIX, and it won't be ever changed (as that would break backward compatibility). So, while 'struct sched_param' is indeed part of the kernel uapi, exposing it the way it's done now creates an issue, and hiding it (like this patch does) fixes that issue, hopefully without creating another one: common userspace software rely on libc headers, and as for "special" software (like libc), it looks like glibc and musl do not rely on kernel headers for 'struct sched_param' definition (but let's Cc their mailing lists in case it's otherwise). The alternative to this patch would be to move struct sched_attr to, say, linux/sched.h, or linux/sched/attr.h (the new file). Oh, and here is the previous attempt to fix the issue: https://lore.kernel.org/all/20200528135552.GA87103@google.com/ While I support Linus arguments, the issue is still here and needs to be fixed. [ mingo: Linus is right, this shouldn't be needed - but on the other hand I agree that this header is not really helpful to user-space as-is. So let's pretend that is only about sched_attr, and call this commit a workaround for user-space breakage that it in reality is ... Also, remove the Fixes tag. ] Change-Id: I3943f8f4a11a9007ccc392de3ece9e62841e8fcb Signed-off-by: Kir Kolyshkin Signed-off-by: Ingo Molnar Cc: Linus Torvalds Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20230808030357.1213829-1-kolyshkin@gmail.com --- include/linux/sched.h | 5 ++++- include/uapi/linux/sched/types.h | 4 ---- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 9fb6635f0bcd..ee54107144dd 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -56,7 +56,6 @@ struct robust_list_head; struct root_domain; struct rq; struct sched_attr; -struct sched_param; struct seq_file; struct sighand_struct; struct signal_struct; @@ -328,6 +327,10 @@ extern struct root_domain def_root_domain; extern struct mutex sched_domains_mutex; #endif +struct sched_param { + int sched_priority; +}; + struct sched_info { #ifdef CONFIG_SCHED_INFO /* Cumulative counters: */ diff --git a/include/uapi/linux/sched/types.h b/include/uapi/linux/sched/types.h index c852153ddb0d..f863e747ff5f 100644 --- a/include/uapi/linux/sched/types.h +++ b/include/uapi/linux/sched/types.h @@ -4,10 +4,6 @@ #include -struct sched_param { - int sched_priority; -}; - #define SCHED_ATTR_SIZE_VER0 48 /* sizeof first published struct */ #define SCHED_ATTR_SIZE_VER1 56 /* add: util_{min,max} */