From 0de5ad2f5083fcf19e579f5a70641e0da0e70dc4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <mdaenzer@redhat.com>
Date: Tue, 18 Feb 2020 19:04:00 +0100
Subject: [PATCH 6/8] util: Change os_same_file_description return type from
 bool to int
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This allows communicating that it wasn't possible to determine whether
the two file descriptors reference the same file description. When
that's the case, log a warning in the amdgpu winsys.

In turn, remove the corresponding debugging output from the fallback
os_same_file_description implementation. It depends on the caller if
false negatives are problematic or not.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3879>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3879>

(cherry picked from commit f5a8958910f53d924d062cbf024cebe4134f757a)

Signed-off-by: Michel Dänzer <mdaenzer@redhat.com>
---
 src/util/os_file.c | 18 +++++++++++-------
 src/util/os_file.h | 10 +++++++---
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/src/util/os_file.c b/src/util/os_file.c
index 128fe872db1..228f1e823c5 100644
--- a/src/util/os_file.c
+++ b/src/util/os_file.c
@@ -133,12 +133,16 @@ os_read_file(const char *filename)
    return buf;
 }
 
-bool
+int
 os_same_file_description(int fd1, int fd2)
 {
    pid_t pid = getpid();
 
-   return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2) == 0;
+   /* Same file descriptor trivially implies same file description */
+   if (fd1 == fd2)
+      return 0;
+
+   return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2);
 }
 
 #else
@@ -152,15 +156,15 @@ os_read_file(const char *filename)
    return NULL;
 }
 
-bool
+int
 os_same_file_description(int fd1, int fd2)
 {
+   /* Same file descriptor trivially implies same file description */
    if (fd1 == fd2)
-      return true;
+      return 0;
 
-   debug_warn_once("Can't tell if different file descriptors reference the same"
-                   " file description, false negatives might cause trouble!\n");
-   return false;
+   /* Otherwise we can't tell */
+   return -1;
 }
 
 #endif
diff --git a/src/util/os_file.h b/src/util/os_file.h
index 1972beba32b..58639476f60 100644
--- a/src/util/os_file.h
+++ b/src/util/os_file.h
@@ -32,10 +32,14 @@ char *
 os_read_file(const char *filename);
 
 /*
- * Returns true if the two file descriptors passed in can be determined to
- * reference the same file description, false otherwise
+ * Try to determine if two file descriptors reference the same file description
+ *
+ * Return values:
+ * - 0:   They reference the same file description
+ * - > 0: They do not reference the same file description
+ * - < 0: Unable to determine whether they reference the same file description
  */
-bool
+int
 os_same_file_description(int fd1, int fd2);
 
 #ifdef __cplusplus
-- 
2.26.2