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Sun, 16 Nov 2025 16:52:54 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: Ag6Jzdul079s Date: Sun, 16 Nov 2025 22:51:42 +0100 From: "Arnd Bergmann" To: "Thomas Gleixner" , LKML Cc: "Mathieu Desnoyers" , "Paul E. McKenney" , "Boqun Feng" , "Jonathan Corbet" , "Prakash Sangappa" , "Madadi Vineeth Reddy" , "K Prateek Nayak" , "Steven Rostedt" , "Sebastian Andrzej Siewior" , Linux-Arch , "Randy Dunlap" , "Peter Zijlstra" , "Christian Brauner" Message-Id: <3bc50dd8-d115-4516-8a21-8313a57f1b40@app.fastmail.com> In-Reply-To: <20251116174750.984829834@linutronix.de> References: <20251116173423.031443519@linutronix.de> <20251116174750.984829834@linutronix.de> Subject: Re: [patch V4 06/12] rseq: Implement sys_rseq_slice_yield() Content-Type: text/plain Content-Transfer-Encoding: 7bit On Sun, Nov 16, 2025, at 21:51, Thomas Gleixner wrote: > 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 > Cc: Arnd Bergmann > Cc: linux-arch@vger.kernel.org > --- > V2: Use the proper name in sys_ni.c and add comment - Prateek I checked that the syscalls are well-formed across all architectures, which is easy here, since there are no arguments. Acked-by: Arnd Bergmann Two minor comments: - Number 470 is also used in Christian Brauner's listns series. Obviously only one of you can claim that number. > +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl > @@ -408,3 +408,4 @@ > 467 n32 open_tree_attr sys_open_tree_attr > 468 n32 file_getattr sys_file_getattr > 469 n32 file_setattr sys_file_setattr > +470 common rseq_slice_yield sys_rseq_slice_yield > --- a/arch/mips/kernel/syscalls/syscall_n64.tbl > +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl > @@ -384,3 +384,4 @@ > 467 n64 open_tree_attr sys_open_tree_attr > 468 n64 file_getattr sys_file_getattr > 469 n64 file_setattr sys_file_setattr > +470 common rseq_slice_yield sys_rseq_slice_yield > --- a/arch/mips/kernel/syscalls/syscall_o32.tbl > +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl > @@ -457,3 +457,4 @@ > 467 o32 open_tree_attr sys_open_tree_attr > 468 o32 file_getattr sys_file_getattr > 469 o32 file_setattr sys_file_setattr > +470 common rseq_slice_yield sys_rseq_slice_yield - These should probably all become 'common' eventually, especially now that the s390 compat syscalls are out of the way, I would like to revisit my series that unifies the tables for syscalls over 402 into a single source file. Until then, it's probably less confusing to keep the format and use n32/n64/o32 here. Arnd