Auto merge of #2874 - rtzoeller:FUTEX_LOCK_PI2, r=JohnTitor

Add FUTEX_LOCK_PI2 on Linux

Tested using a modified version of the [linux-futex crate](https://github.com/m-ou-se/linux-futex/).

Author: bors

libc-test/build.rs

@@ -3187,6 +3187,9 @@ fn test_linux(target: &str) {
             // present in recent kernels only
             "PR_PAC_SET_ENABLED_KEYS" | "PR_PAC_GET_ENABLED_KEYS" => true,
 
+            // Added in Linux 5.14
+            "FUTEX_LOCK_PI2" => true,
+
             _ => false,
         }
     });

libc-test/semver/linux.txt

@@ -599,6 +599,7 @@ FUTEX_CMP_REQUEUE
 FUTEX_CMP_REQUEUE_PI
 FUTEX_FD
 FUTEX_LOCK_PI
+FUTEX_LOCK_PI2
 FUTEX_PRIVATE_FLAG
 FUTEX_REQUEUE
 FUTEX_TRYLOCK_PI

src/unix/linux_like/linux/mod.rs

@@ -3074,6 +3074,7 @@ pub const FUTEX_WAIT_BITSET: ::c_int = 9;
 pub const FUTEX_WAKE_BITSET: ::c_int = 10;
 pub const FUTEX_WAIT_REQUEUE_PI: ::c_int = 11;
 pub const FUTEX_CMP_REQUEUE_PI: ::c_int = 12;
+pub const FUTEX_LOCK_PI2: ::c_int = 13;
 
 pub const FUTEX_PRIVATE_FLAG: ::c_int = 128;
 pub const FUTEX_CLOCK_REALTIME: ::c_int = 256;