From 6563803ed3ea02d48ad9d853bad502633ae970af Mon Sep 17 00:00:00 2001
From: varkor <github@varkor.com>
Date: Thu, 9 Aug 2018 19:38:41 +0100
Subject: [PATCH 1/2] Don't set rlimit to a lower value than the current

---
 src/librustc_driver/lib.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 556ee9f5716ea..f34c4158923d6 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -1512,7 +1512,7 @@ pub fn in_named_rustc_thread<F, R>(name: String, f: F) -> Result<R, Box<dyn Any
             true
         } else if rlim.rlim_max < STACK_SIZE as libc::rlim_t {
             true
-        } else {
+        } else if rlim.rlim_cur < STACK_SIZE as libc::rlim_t {
             std::rt::deinit_stack_guard();
             rlim.rlim_cur = STACK_SIZE as libc::rlim_t;
             if libc::setrlimit(libc::RLIMIT_STACK, &mut rlim) != 0 {
@@ -1524,6 +1524,8 @@ pub fn in_named_rustc_thread<F, R>(name: String, f: F) -> Result<R, Box<dyn Any
                 std::rt::update_stack_guard();
                 false
             }
+        } else {
+            false
         }
     };
 

From 82a704abe70c6f3ee4577254a963566639f4720c Mon Sep 17 00:00:00 2001
From: varkor <github@varkor.com>
Date: Thu, 9 Aug 2018 19:40:49 +0100
Subject: [PATCH 2/2] Add a safety check for compiletest rlimit

---
 src/tools/compiletest/src/raise_fd_limit.rs | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/tools/compiletest/src/raise_fd_limit.rs b/src/tools/compiletest/src/raise_fd_limit.rs
index 220082799a8b0..d1071231530d6 100644
--- a/src/tools/compiletest/src/raise_fd_limit.rs
+++ b/src/tools/compiletest/src/raise_fd_limit.rs
@@ -57,14 +57,16 @@ pub unsafe fn raise_fd_limit() {
         panic!("raise_fd_limit: error calling getrlimit: {}", err);
     }
 
-    // Bump the soft limit to the smaller of kern.maxfilesperproc and the hard
-    // limit
-    rlim.rlim_cur = cmp::min(maxfiles as libc::rlim_t, rlim.rlim_max);
+    // Make sure we're only ever going to increase the rlimit.
+    if rlim.rlim_cur < maxfiles as libc::rlim_t {
+        // Bump the soft limit to the smaller of kern.maxfilesperproc and the hard limit.
+        rlim.rlim_cur = cmp::min(maxfiles as libc::rlim_t, rlim.rlim_max);
 
-    // Set our newly-increased resource limit
-    if libc::setrlimit(libc::RLIMIT_NOFILE, &rlim) != 0 {
-        let err = io::Error::last_os_error();
-        panic!("raise_fd_limit: error calling setrlimit: {}", err);
+        // Set our newly-increased resource limit.
+        if libc::setrlimit(libc::RLIMIT_NOFILE, &rlim) != 0 {
+            let err = io::Error::last_os_error();
+            panic!("raise_fd_limit: error calling setrlimit: {}", err);
+        }
     }
 }