Mesa (staging/20.0): util: Change os_same_file_description return type from bool to int

[GitLab Mirror]

Module: Mesa
Branch: staging/20.0
Commit: 1abcfb02a86af11ed674bd30ebc9d333aa09cea9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1abcfb02a86af11ed674bd30ebc9d333aa09cea9

Author: Michel Dänzer <mdaenzer at redhat.com>
Date:   Tue Feb 18 19:04:00 2020 +0100

util: Change os_same_file_description return type from bool to int

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 at engestrom.ch>
Reviewed-by: Marek Olšák <marek.olsak at 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)

---

 .pick_status.json                             |  2 +-
 src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c | 15 ++++++++++++++-
 src/util/os_file.c                            | 18 +++++++++++-------
 src/util/os_file.h                            | 10 +++++++---
 4 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index 14baf637647..ca9b2c0492c 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -39415,7 +39415,7 @@
         "description": "util: Change os_same_file_description return type from bool to int",
         "nominated": false,
         "nomination_type": null,
-        "resolution": 4,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": null
     },
diff --git a/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c b/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c
index 4bbd50664ba..8b56f69568d 100644
--- a/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c
+++ b/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c
@@ -31,6 +31,7 @@
 #include "amdgpu_public.h"
 
 #include "util/os_file.h"
+#include "util/os_misc.h"
 #include "util/u_cpu_detect.h"
 #include "util/u_hash_table.h"
 #include "util/hash_table.h"
@@ -380,13 +381,25 @@ amdgpu_winsys_create(int fd, const struct pipe_screen_config *config,
 
       simple_mtx_lock(&aws->sws_list_lock);
       for (sws_iter = aws->sws_list; sws_iter; sws_iter = sws_iter->next) {
-         if (os_same_file_description(sws_iter->fd, ws->fd)) {
+         r = os_same_file_description(sws_iter->fd, ws->fd);
+
+         if (r == 0) {
             close(ws->fd);
             FREE(ws);
             ws = sws_iter;
             pipe_reference(NULL, &ws->reference);
             simple_mtx_unlock(&aws->sws_list_lock);
             goto unlock;
+         } else if (r < 0) {
+            static bool logged;
+
+            if (!logged) {
+               os_log_message("amdgpu: os_same_file_description couldn't "
+                              "determine if two DRM fds reference the same "
+                              "file description.\n"
+                              "If they do, bad things may happen!\n");
+               logged = true;
+            }
          }
       }
       simple_mtx_unlock(&aws->sws_list_lock);
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