multithread: doc improvements

README.adoc

@@ -10579,7 +10579,7 @@ cat /proc/cpuinfo
 getconf _NPROCESSORS_CONF
 ....
 
-====== Number of cores in QEMU user mode
+====== QEMU user mode multithreading
 
 TODO why in <<user-mode-simulation>> QEMU always shows the number of cores of the host. E.g., both of the following output the same as `nproc` on the host:
 
@@ -10602,9 +10602,9 @@ Remember <<qemu-user-mode-does-not-show-stdout-immediately>> though.
 
 At 369a47fc6e5c2f4a7f911c1c058b6088f8824463 + 1 QEMU appears to spawn 3 host threads plus one for every new guest thread created.  Remember that link:userland/posix/pthread_count.c[] spawns N + 1 total threads if you count the `main` thread.
 
-====== Number of cores in gem5 user mode
+====== gem5 syscall emulation multithreading
 
-gem5 user mode multi core has been particularly flaky compared <<number-of-cores-in-qemu-user-mode,to QEMU's>>.
+gem5 user mode multithreading has been particularly flaky compared <<qemu-user-mode-multithreading,to QEMU's>>.
 
 You have the limitation that you must have at least one core per guest thread, otherwise `pthread_create` fails. For example:
 
@@ -13110,8 +13110,8 @@ The following sections are related to multithreading in userland:
 ** <<x86-thread-synchronization-primitives>>
 ** <<arm-lse>>
 * emulator topics:
-** <<number-of-cores-in-qemu-user-mode>>
-** <<number-of-cores-in-gem5-user-mode>>
+** <<qemu-user-mode-multithreading>>
+** <<gem5-syscall-emulation-multithreading>>
 
 === C debugging
 

userland/posix/pthread_self.c

@@ -3,10 +3,16 @@
  *
  * https://cirosantilli.com/linux-kernel-module-cheat#pthreads
  *
+ * Usage:
+ *
+ * ....
+ * ./pthread_self.out [nthreads]
+ * ....
+ *
  * Sample usage:
  *
  * ....
- * ./pthread_tid.out 4
+ * ./pthread_self.out [nthreads]
  * ....
  *
  * Sample output: