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diff --git a/man2/getpid.2 b/man2/getpid.2
index ca9b38d0ab..24f74dfe9c 100644
--- a/man2/getpid.2
+++ b/man2/getpid.2
@@ -22,55 +22,76 @@
 .\" the source, must acknowledge the copyright and authors of this work.
 .\" %%%LICENSE_END
 .\"
-.TH GETPID 2 2015-03-29 "Linux" "Linux Programmer's Manual"
+.TH GETPID 2 2019-03-06 "Linux" "Linux Programmer's Manual"
 .SH NAME
 getpid, getppid \- get process identification
 .SH SYNOPSIS
 .B #include <sys/types.h>
 .br
 .B #include <unistd.h>
-.sp
+.PP
 .B pid_t getpid(void);
 .br
 .B pid_t getppid(void);
 .SH DESCRIPTION
 .BR getpid ()
-returns the process ID of the calling process.
+returns the process ID (PID) of the calling process.
 (This is often used by
 routines that generate unique temporary filenames.)
-
+.PP
 .BR getppid ()
 returns the process ID of the parent of the calling process.
+This will be either the ID of the process that created this process using
+.BR fork (),
+or, if that process has already terminated,
+the ID of the process to which this process has been reparented (either
+.BR init (1)
+or a "subreaper" process defined via the
+.BR prctl (2)
+.BR PR_SET_CHILD_SUBREAPER
+operation).
 .SH ERRORS
 These functions are always successful.
 .SH CONFORMING TO
-POSIX.1-2001, 4.3BSD, SVr4.
+POSIX.1-2001, POSIX.1-2008, 4.3BSD, SVr4.
 .SH NOTES
 If the caller's parent is in a different PID namespace (see
 .BR pid_namespaces (7)),
 .BR getppid ()
 returns 0.
+.PP
+From a kernel perspective,
+the PID (which is shared by all of the threads in a multithreaded process)
+is sometimes also known as the thread group ID (TGID).
+This contrasts with the kernel thread ID (TID),
+which is unique for each thread.
+For further details, see
+.BR gettid (2)
+and the discussion of the
+.BR CLONE_THREAD
+flag in
+.BR clone (2).
 .\"
-.SS C library/kernel ABI differences
-Since glibc version 2.3.4,
+.SS C library/kernel differences
+From glibc version 2.3.4 up to and including version 2.24,
 the glibc wrapper function for
 .BR getpid ()
-caches PIDs,
-so as to avoid additional system calls when a process calls
+cached PIDs,
+with the goal of avoiding additional system calls when a process calls
 .BR getpid ()
 repeatedly.
-Normally this caching is invisible,
-but its correct operation relies on support in the wrapper functions for
+Normally this caching was invisible,
+but its correct operation relied on support in the wrapper functions for
 .BR fork (2),
 .BR vfork (2),
 and
 .BR clone (2):
-if an application bypasses the glibc wrappers for these system calls by using
+if an application bypassed the glibc wrappers for these system calls by using
 .BR syscall (2),
 then a call to
 .BR getpid ()
-in the child will return the wrong value
-(to be precise: it will return the PID of the parent process).
+in the child would return the wrong value
+(to be precise: it would return the PID of the parent process).
 .\" The following program demonstrates this "feature":
 .\"
 .\" #define _GNU_SOURCE
@@ -96,16 +117,45 @@ in the child will return the wrong value
 .\"    }
 .\"    wait(NULL);
 .\"}
-See also
-.BR clone (2)
-for discussion of a case where
+In addition, there were cases where
 .BR getpid ()
-may return the wrong value even when invoking
+could return the wrong value even when invoking
 .BR clone (2)
 via the glibc wrapper function.
+(For a discussion of one such case, see BUGS in
+.BR clone (2).)
+Furthermore, the complexity of the caching code had been
+the source of a few bugs within glibc over the years.
+.PP
+Because of the aforementioned problems,
+since glibc version 2.25, the PID cache is removed:
+.\" commit c579f48edba88380635ab98cb612030e3ed8691e
+.\" https://sourceware.org/glibc/wiki/Release/2.25#pid_cache_removal
+calls to
+.BR getpid ()
+always invoke the actual system call, rather than returning a cached value.
+.\" FIXME .
+.\" Review progress of https://bugzilla.redhat.com/show_bug.cgi?id=1469757
+.PP
+On Alpha, instead of a pair of
+.BR getpid ()
+and
+.BR getppid ()
+system calls, a single
+.BR getxpid ()
+system call is provided, which returns a pair of PID and parent PID.
+The glibc
+.BR getpid ()
+and
+.BR getppid ()
+wrapper functions transparently deal with this.
+See
+.BR syscall (2)
+for details regarding register mapping.
 .SH SEE ALSO
 .BR clone (2),
 .BR fork (2),
+.BR gettid (2),
 .BR kill (2),
 .BR exec (3),
 .BR mkstemp (3),