@@ -62,6 +62,8 @@ argument is a bit mask that can contain zero or more of the following values
 ORed together:
 .TP
 .B GRND_RANDOM
+.\" commit 48446f198f9adcb499b30332488dfd5bc3f176f6
+Ignored since Linux 5.6.
 If this bit is set, then random bytes are drawn from the
 .I random
 source

@@ -103,6 +105,13 @@ does not block in these cases, but instead immediately returns \-1 with
 .I errno
 set to
 .BR EAGAIN .
+.TP GRND_INSECURE
+.\" commit 75551dbf112c992bc6c99a972990b3f272247e23
+Added in Linux 5.6.
+Request best-effort, non-cryptographic-quality random bytes.
+If this bit is set, then
+.BR getrandom ()
+will never block or fail due to a lack of entropy.
 .SH RETURN VALUE
 On success,
 .BR getrandom ()

@@ -56,17 +56,29 @@ or
 .I /dev/random
 instead.
 .P
-The
+.\" commit 30c08efec8884fb106b8e57094baa51bb4c44e32
+As of Linux 5.6,
+.I /dev/random
+is identical to
+.I /dev/urandom
+except that it blocks during early boot.
+A jitter-based seeding technique added in Linux 5.4 should help reduce
+block time.
+.\" commit 50ee7529ec4500c88f8664560770a7a1b65db72b
+.P
+The pre-Linux 5.6
 .I /dev/random
-device is a legacy interface which dates back to
+device was a legacy interface which dates back to
 a time where the cryptographic primitives used in the implementation
 of
 .I /dev/urandom
 were not widely trusted.
-It will return random bytes only within the estimated number of
-bits of fresh noise in the entropy pool, blocking if necessary.
+It would return random bytes only within the estimated number of bits of fresh
+noise in the entropy pool, blocking until additional environmental noise is
+gathered.
+This old
 .I /dev/random
-is suitable for applications that need
+was suitable for applications that need
 high quality randomness, and can afford indeterminate delays.
 .P
 When the entropy pool is empty, reads from

@@ -121,7 +133,8 @@ A
 .BR read (2)
 from
 .I /dev/random
-will return at most 512 bytes
+has the same maximum size since Linux 5.6. Between Linux 3.16 and 5.5,
+the maximum size was 512 bytes. (340 bytes before Linux 2.6.12)
 .\" SEC_XFER_SIZE in drivers/char/random.c
 (340 bytes before Linux 2.6.12).
 .P

@@ -133,7 +146,7 @@ will update the
 entropy pool with the data written, but this will not result in a
 higher entropy count.
 This means that it will impact the contents
-read from both files, but it will not make reads from
+read from both files, but it will not make reads from a pre-Linux 5.6
 .I /dev/random
 faster.
 .SS Usage

@@ -158,7 +171,7 @@ soon as it is reloaded in the boot sequence, and perfectly adequate for
 network encryption session keys.
 (All major Linux distributions have saved the seed file across reboots
 since 2000 at least.)
-Since reads from
+Since reads from a pre-Linux 5.6
 .I /dev/random
 may block, users will usually want to open it in nonblocking mode
 (or perform a read with timeout),

@@ -262,6 +275,7 @@ It contains the value 4096.
 .RE
 .TP
 .I read_wakeup_threshold
+Removed in Linux 5.6.
 This file
 contains the number of bits of entropy required for waking up processes
 that sleep waiting for entropy from

@@ -54,17 +54,16 @@ The kernel collects bits of entropy from the environment.
 When a sufficient number of random bits has been collected, the
 entropy pool is considered to be initialized.
 .SS Choice of random source
-Unless you are doing long-term key generation (and most likely not even
-then), you probably shouldn't be reading from the
+Unless your program may run at early-boot, before the entropy pool
+is initialized, there is no longer any palpable difference between
 .I /dev/random
-device or employing
-.BR getrandom (2)
-with the
-.B GRND_RANDOM
-flag.
-Instead, either read from the
+and
+.I /dev/urandom
+since Linux 5.6. (See the table below.)
+.PP.
+On older kernels, either read from the
 .I /dev/urandom
-device or employ
+device or (especially if you are concerned with early boot) employ
 .BR getrandom (2)
 without the
 .B GRND_RANDOM

@@ -117,9 +116,9 @@ T}
 T{
 .I /dev/random
 T}	T{
-Blocking pool
+CSPRNG output
 T}	T{
-If entropy too low, blocks until there is enough entropy again
+Never blocks
 T}	T{
 Blocks until enough entropy gathered
 T}

@@ -144,17 +143,6 @@ Blocks until pool ready
 T}
 T{
 .BR getrandom ()
-.B GRND_RANDOM
-T}	T{
-Same as
-.I /dev/random
-T}	T{
-If entropy too low, blocks until there is enough entropy again
-T}	T{
-Blocks until pool ready
-T}
-T{
-.BR getrandom ()
 .B GRND_NONBLOCK
 T}	T{
 Same as

@@ -166,21 +154,45 @@ T}	T{
 T}
 T{
 .BR getrandom ()
-.B GRND_RANDOM
-+
-.B GRND_NONBLOCK
+.B GRND_INSECURE
 T}	T{
 Same as
-.I /dev/random
+.I /dev/urandom
 T}	T{
-.B EAGAIN
-if not enough entropy available
+Never blocks
 T}	T{
-.B EAGAIN
+Returns output from uninitialized CSPRNG (may be low entropy and unsuitable for cryptography)
 T}
 .TE
 .ad
 .\"
+.SS The old blocking pool
+The above table describes the behavior of the interfaces since
+Linux 5.6.  In older kernels, the
+.I /dev/random
+used a separate blocking pool, and
+.BR getrandom ()
+had a
+.B GRND_RANDOM
+flag for reading from the blocking pool.
+.\"
+.PP
+The older blocking pool was a vestige of a time when the CSPRNG
+was not trusted.
+It assumed that entropy can run out by reading the CSPRNG.
+This has never been the case.
+Instead, programs using
+.B GRND_RANDOM
+and
+.I /dev/random
+had to deal with operations blocking indefinitely.
+Furthermore, dealing with the partially fulfilled
+requests that can occur when using
+.B GRND_RANDOM
+or when reading from
+.I /dev/random
+increases code complexity.
+.\"
 .SS Generating cryptographic keys
 The amount of seed material required to generate a cryptographic key
 equals the effective key size of the key.