arch_prctl.2: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/arch_prctl.2

@@ -28,9 +28,8 @@ arch_prctl \- set architecture-specific thread state
 .SH SYNOPSIS
 .nf
 .B #include <asm/prctl.h>
-.br
 .B #include <sys/prctl.h>
-.sp
+.PP
 .BI "int arch_prctl(int " code ", unsigned long " addr );
 .BI "int arch_prctl(int " code ", unsigned long *" addr );
 .fi
@@ -107,12 +106,12 @@ to be portable.
 .SH NOTES
 .BR arch_prctl ()
 is supported only on Linux/x86-64 for 64-bit programs currently.
-
+.PP
 The 64-bit base changes when a new 32-bit segment selector is loaded.
-
+.PP
 .B ARCH_SET_GS
 is disabled in some kernels.
-
+.PP
 Context switches for 64-bit segment bases are rather expensive.
 As an optimization, if a 32-bit TLS base address is used,
 .BR arch_prctl ()
@@ -124,19 +123,19 @@ Memory in the first 2GB of address space can be allocated by using
 with the
 .B MAP_32BIT
 flag.
-
+.PP
 Because of the aforementioned optimization, using
 .BR arch_prctl ()
 and
 .BR set_thread_area (2)
 in the same thread is dangerous, as they may overwrite each other's
 TLS entries.
-
+.PP
 As of version 2.7, glibc provides no prototype for
 .BR arch_prctl ().
 You have to declare it yourself for now.
 This may be fixed in future glibc versions.
-
+.PP
 .I FS
 may be already used by the threading library.
 Programs that use
@@ -147,5 +146,5 @@ directly are very likely to crash.
 .BR modify_ldt (2),
 .BR prctl (2),
 .BR set_thread_area (2)
-
+.PP
 AMD X86-64 Programmer's manual