Hello Brice,
On 5/5/19 12:19 PM, Brice Goglin wrote:
sched_setaffinity.2: sched_getaffinity returns the number of bytes copied
On success, it returns min(len, cpumask_size()) where len is
the output buffer size (see the syscall definition in kernel/sched/core.c).
Signed-off-by: Brice Goglin <Brice.Goglin@xxxxxxxx>
---
man2/sched_setaffinity.2 | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/man2/sched_setaffinity.2 b/man2/sched_setaffinity.2
index 74bbde81c..277edd0fb 100644
--- a/man2/sched_setaffinity.2
+++ b/man2/sched_setaffinity.2
@@ -107,9 +107,9 @@ is zero, then the mask of the calling thread is returned.
.SH RETURN VALUE
On success,
.BR sched_setaffinity ()
-and
+returns 0, while
.BR sched_getaffinity ()
-return 0.
+returns the number of bytes copied to the destination mask.
On error, \-1 is returned, and
.I errno
is set appropriately.
Thanks for adding some detail. However, did you take a look at the
glibc wrapper, and also this text in the manual page:
C library/kernel differences
[...] On success, the raw sched_getaffinity() system call
returns the size (in bytes) of the cpumask_t data type that is
used internally by the kernel to represent the CPU set bit mask.
Of course, looking at your patch, it's clear that that text is no longer
fully accurate (since Linux 2.6.34, commit cd3d8031eb4311e). I've now
adjusted it to say:
On success, the raw sched_getaffinity() system call returns the
number of bytes placed copied into the mask buffer; this will be
the minimum of cpusetsize and the size (in bytes) of the cpumask_t
data type that is used internally by the kernel to represent the
CPU set bit mask.
Thanks for report!
Cheers,
Michael
