On Mon, Jan 22, 2018 at 01:16:25PM +0000, Eugene Syromyatnikov wrote: > On Sat, Jan 20, 2018 at 11:41 AM, Heiko Carstens > <heiko.carstens@xxxxxxxxxx> wrote: > > If you now document the above people will start using the system call with > > only one parameter which isn't backwards compatible. > > > > I'd rather add the second parameter again to the system call so that code > > stays backwards compatible. > > Well, it ought to be documented somehow, especially if the syscall > parameter will be added back, as there could be situation where > application gets successful return code for the call non-zero value of > the second argument and gets no signals as it is the one of the kernel > releases where this parameter was removed. I can update the patch to > reflect this once the patch that returns the second argument reaches > the kernel tree. So, I think something like the below should be ok: >From 6c7e2113c62fbb95662fba03f7fa298f4b737c1f Mon Sep 17 00:00:00 2001 From: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Date: Wed, 31 Jan 2018 08:15:31 +0100 Subject: [PATCH] s390_runtime_instr.2: document signum argument behavior change Document that the signum argument is ignored in newer kernels, but that user space should pass a valid real-time signal number for backwards compatibility. Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx> --- man2/s390_runtime_instr.2 | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/man2/s390_runtime_instr.2 b/man2/s390_runtime_instr.2 index 18c2c0763eed..d5790e10f222 100644 --- a/man2/s390_runtime_instr.2 +++ b/man2/s390_runtime_instr.2 @@ -47,10 +47,9 @@ argument controls whether run-time instrumentation is started .PP The .IR signum -argument specifies the number of a real-time signal. -The real-time signal is sent to the thread if the run-time instrumentation -buffer is full or if the run-time-instrumentation-halted interrupt -occurred. +argument specifies the number of a real-time signal. This argument has no +effect, since support for signalling was never used and kernel support was +removed. .SH RETURN VALUE On success, .BR s390_runtime_instr () @@ -67,9 +66,16 @@ is set to one of the error codes listed below. .B EINVAL The value specified in .IR command -is not a valid command or the value specified in +is not a valid command. +.TP +.B EINVAL +The value specified in .IR signum -is not a real-time signal number. +is not a real-time signal number. With Linux 4.4 and newer kernel versions, +the +.IR signum +argument has no effect, so that an invalid signal number will not result in an +error. .TP .B ENOMEM Allocating memory for the run-time instrumentation control block failed. @@ -85,6 +91,12 @@ The run-time instrumentation facility is available beginning with System z EC12. Glibc does not provide a wrapper for this system call, use .BR syscall (2) to call it. +.PP +Support for signalling was removed with Linux 4.4. With Linux 4.4 +also the check if +.IR signum +is a valid real-time signal was removed. For backwards compatibility with old +kernels it is recommended to pass a valid real-time signal number. .SH SEE ALSO .BR syscall (2), .BR signal (7) -- 2.13.5 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
