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Message-ID: <176907696439.510.7942680473551218935.tip-bot2@tip-bot2>
Date: Thu, 22 Jan 2026 10:16:04 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Arnd Bergmann <arnd@...db.de>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] rseq: Implement sys_rseq_slice_yield()
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 99d2592023e5d0a31f5f5a83c694df48239a1e6c
Gitweb: https://git.kernel.org/tip/99d2592023e5d0a31f5f5a83c694df48239a1e6c
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 15 Dec 2025 17:52:15 +01:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 22 Jan 2026 11:11:17 +01:00
rseq: Implement sys_rseq_slice_yield()
Provide a new syscall which has the only purpose to yield the CPU after the
kernel granted a time slice extension.
sched_yield() is not suitable for that because it unconditionally
schedules, but the end of the time slice extension is not required to
schedule when the task was already preempted. This also allows to have a
strict check for termination to catch user space invoking random syscalls
including sched_yield() from a time slice extension region.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Acked-by: Arnd Bergmann <arnd@...db.de>
Link: https://patch.msgid.link/20251215155708.929634896@linutronix.de
---
arch/alpha/kernel/syscalls/syscall.tbl | 1 +-
arch/arm/tools/syscall.tbl | 1 +-
arch/arm64/tools/syscall_32.tbl | 1 +-
arch/m68k/kernel/syscalls/syscall.tbl | 1 +-
arch/microblaze/kernel/syscalls/syscall.tbl | 1 +-
arch/mips/kernel/syscalls/syscall_n32.tbl | 1 +-
arch/mips/kernel/syscalls/syscall_n64.tbl | 1 +-
arch/mips/kernel/syscalls/syscall_o32.tbl | 1 +-
arch/parisc/kernel/syscalls/syscall.tbl | 1 +-
arch/powerpc/kernel/syscalls/syscall.tbl | 1 +-
arch/s390/kernel/syscalls/syscall.tbl | 1 +-
arch/sh/kernel/syscalls/syscall.tbl | 1 +-
arch/sparc/kernel/syscalls/syscall.tbl | 1 +-
arch/x86/entry/syscalls/syscall_32.tbl | 1 +-
arch/x86/entry/syscalls/syscall_64.tbl | 1 +-
arch/xtensa/kernel/syscalls/syscall.tbl | 1 +-
include/linux/rseq_types.h | 2 ++-
include/linux/syscalls.h | 1 +-
include/uapi/asm-generic/unistd.h | 5 ++++-
kernel/rseq.c | 21 ++++++++++++++++++++-
kernel/sys_ni.c | 1 +-
scripts/syscall.tbl | 1 +-
22 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 3fed974..f31b7af 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -510,3 +510,4 @@
578 common file_getattr sys_file_getattr
579 common file_setattr sys_file_setattr
580 common listns sys_listns
+581 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index fd09afa..94351e2 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -485,3 +485,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/arm64/tools/syscall_32.tbl b/arch/arm64/tools/syscall_32.tbl
index 8cdfe5d..62d93d8 100644
--- a/arch/arm64/tools/syscall_32.tbl
+++ b/arch/arm64/tools/syscall_32.tbl
@@ -482,3 +482,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index 871a5d6..2489342 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -470,3 +470,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 022fc85..223d263 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -476,3 +476,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 8cedc83..7430714 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -409,3 +409,4 @@
468 n32 file_getattr sys_file_getattr
469 n32 file_setattr sys_file_setattr
470 n32 listns sys_listns
+471 n32 rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 9b92bdd..630aab9 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -385,3 +385,4 @@
468 n64 file_getattr sys_file_getattr
469 n64 file_setattr sys_file_setattr
470 n64 listns sys_listns
+471 n64 rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index f810b8a..1286531 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -458,3 +458,4 @@
468 o32 file_getattr sys_file_getattr
469 o32 file_setattr sys_file_setattr
470 o32 listns sys_listns
+471 o32 rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 39bdaca..f6e2d03 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -469,3 +469,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index ec4458c..4fcc7c5 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -561,3 +561,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 nospu rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 417ed16..09a7ef0 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -397,3 +397,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 969c113..70b315c 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -474,3 +474,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 39aa26b..d5b1a71 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -516,3 +516,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index e979a3e..f832ebd 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -476,3 +476,4 @@
468 i386 file_getattr sys_file_getattr
469 i386 file_setattr sys_file_setattr
470 i386 listns sys_listns
+471 i386 rseq_slice_yield sys_rseq_slice_yield
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 8a4ac48..524155d 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -395,6 +395,7 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
#
# Due to a historical design error, certain syscalls are numbered differently
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 438a3b1..a9bca4e 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -441,3 +441,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
diff --git a/include/linux/rseq_types.h b/include/linux/rseq_types.h
index 67e40c0..8c540e7 100644
--- a/include/linux/rseq_types.h
+++ b/include/linux/rseq_types.h
@@ -89,9 +89,11 @@ union rseq_slice_state {
/**
* struct rseq_slice - Status information for rseq time slice extension
* @state: Time slice extension state
+ * @yielded: Indicator for rseq_slice_yield()
*/
struct rseq_slice {
union rseq_slice_state state;
+ u8 yielded;
};
/**
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index cf84d98..6c8a570 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -961,6 +961,7 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,
unsigned mask, struct statx __user *buffer);
asmlinkage long sys_rseq(struct rseq __user *rseq, uint32_t rseq_len,
int flags, uint32_t sig);
+asmlinkage long sys_rseq_slice_yield(void);
asmlinkage long sys_open_tree(int dfd, const char __user *path, unsigned flags);
asmlinkage long sys_open_tree_attr(int dfd, const char __user *path,
unsigned flags,
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 942370b..a627acc 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -860,8 +860,11 @@ __SYSCALL(__NR_file_setattr, sys_file_setattr)
#define __NR_listns 470
__SYSCALL(__NR_listns, sys_listns)
+#define __NR_rseq_slice_yield 471
+__SYSCALL(__NR_rseq_slice_yield, sys_rseq_slice_yield)
+
#undef __NR_syscalls
-#define __NR_syscalls 471
+#define __NR_syscalls 472
/*
* 32 bit systems traditionally used different
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 09848bb..d8e1992 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -553,6 +553,27 @@ die:
return -EFAULT;
}
+/**
+ * sys_rseq_slice_yield - yield the current processor side effect free if a
+ * task granted with a time slice extension is done with
+ * the critical work before being forced out.
+ *
+ * Return: 1 if the task successfully yielded the CPU within the granted slice.
+ * 0 if the slice extension was either never granted or was revoked by
+ * going over the granted extension, using a syscall other than this one
+ * or being scheduled out earlier due to a subsequent interrupt.
+ *
+ * The syscall does not schedule because the syscall entry work immediately
+ * relinquishes the CPU and schedules if required.
+ */
+SYSCALL_DEFINE0(rseq_slice_yield)
+{
+ int yielded = !!current->rseq.slice.yielded;
+
+ current->rseq.slice.yielded = 0;
+ return yielded;
+}
+
static int __init rseq_slice_cmdline(char *str)
{
bool on;
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index bf5d05c..add3032 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -390,6 +390,7 @@ COND_SYSCALL(setuid16);
/* restartable sequence */
COND_SYSCALL(rseq);
+COND_SYSCALL(rseq_slice_yield);
COND_SYSCALL(uretprobe);
COND_SYSCALL(uprobe);
diff --git a/scripts/syscall.tbl b/scripts/syscall.tbl
index e74868b..7a42b32 100644
--- a/scripts/syscall.tbl
+++ b/scripts/syscall.tbl
@@ -411,3 +411,4 @@
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common listns sys_listns
+471 common rseq_slice_yield sys_rseq_slice_yield
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