On Wed, Jan 31, 2018 at 7:20 AM, Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote: > 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 > Acked-by: Eugene Syromyatnikov <evgsyr@xxxxxxxxx> -- Eugene Syromyatnikov mailto:evgsyr@xxxxxxxxx xmpp:esyr@jabber.{ru|org} -- 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
