[Git][ghc/ghc][wip/backports-8.8] 3 commits: Rts: show errno on failure (#18033)

[Ben Gamari]

Ben Gamari pushed to branch wip/backports-8.8 at Glasgow Haskell Compiler / GHC


Commits:
66c1cf35 by Sylvain Henry at 2020-05-27T22:05:33-04:00
Rts: show errno on failure (#18033)

(cherry picked from commit 4875d419ba066e479f7ac07f8b39ebe10c855859)

- - - - -
2efbf38f by Ben Gamari at 2020-05-27T22:05:58-04:00
rts: Make non-existent linker search path merely a warning

As noted in #18105, previously this resulted in a rather intrusive error
message. This is in contrast to the general expectation that search
paths are merely places to look, not places that must exist.

Fixes #18105.

(cherry picked from commit 24af9f30681444380c25465f555599da563713cb)

- - - - -
df9671ef by Sylvain Henry at 2020-05-27T22:06:55-04:00
RTS: workaround a Linux kernel bug in timerfd

Reading a timerfd may return 0: https://lkml.org/lkml/2019/8/16/335.

This is currently undocumented behavior and documentation "won't happen
anytime soon" (https://lkml.org/lkml/2020/2/13/295).

With this patch, we just ignore the result instead of crashing. It may
fix #18033 but we can't be sure because we don't have enough
information.

See also this discussion about the kernel bug:
https://github.com/Azure/sonic-swss-common/pull/302/files/1f070e7920c2e5d63316c0105bf4481e73d72dc9

(cherry picked from commit 12789d3ac30dd90f77593e99ef51e54b14fbf556)

- - - - -


2 changed files:

- rts/linker/PEi386.c
- rts/posix/itimer/Pthread.c


Changes:

=====================================
rts/linker/PEi386.c
=====================================
@@ -769,12 +769,12 @@ HsPtr addLibrarySearchPath_PEi386(pathchar* dll_path)
     WCHAR* abs_path = malloc(sizeof(WCHAR) * init_buf_size);
     DWORD wResult = GetFullPathNameW(dll_path, bufsize, abs_path, NULL);
     if (!wResult){
-        sysErrorBelch("addLibrarySearchPath[GetFullPathNameW]: %" PATH_FMT " (Win32 error %lu)", dll_path, GetLastError());
+        IF_DEBUG(linker, debugBelch("addLibrarySearchPath[GetFullPathNameW]: %" PATH_FMT " (Win32 error %lu)", dll_path, GetLastError()));
     }
     else if (wResult > init_buf_size) {
         abs_path = realloc(abs_path, sizeof(WCHAR) * wResult);
         if (!GetFullPathNameW(dll_path, bufsize, abs_path, NULL)) {
-            sysErrorBelch("addLibrarySearchPath[GetFullPathNameW]: %" PATH_FMT " (Win32 error %lu)", dll_path, GetLastError());
+            IF_DEBUG(linker, debugBelch("addLibrarySearchPath[GetFullPathNameW]: %" PATH_FMT " (Win32 error %lu)", dll_path, GetLastError()));
         }
     }
 


=====================================
rts/posix/itimer/Pthread.c
=====================================
@@ -109,22 +109,30 @@ static void *itimer_thread_func(void *_handle_tick)
 
     timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
     if (timerfd == -1) {
-        barf("timerfd_create");
+        barf("timerfd_create: %s", strerror(errno));
     }
     if (!TFD_CLOEXEC) {
         fcntl(timerfd, F_SETFD, FD_CLOEXEC);
     }
     if (timerfd_settime(timerfd, 0, &it, NULL)) {
-        barf("timerfd_settime");
+        barf("timerfd_settime: %s", strerror(errno));
     }
 #endif
 
     while (!exited) {
         if (USE_TIMERFD_FOR_ITIMER) {
-            if (read(timerfd, &nticks, sizeof(nticks)) != sizeof(nticks)) {
-                if (errno != EINTR) {
-                    barf("Itimer: read(timerfd) failed");
-                }
+            ssize_t r = read(timerfd, &nticks, sizeof(nticks));
+            if ((r == 0) && (errno == 0)) {
+               /* r == 0 is expected only for non-blocking fd (in which case
+                * errno should be EAGAIN) but we use a blocking fd.
+                *
+                * Due to a kernel bug (cf https://lkml.org/lkml/2019/8/16/335)
+                * on some platforms we could see r == 0 and errno == 0.
+                */
+               IF_DEBUG(scheduler, debugBelch("read(timerfd) returned 0 with errno=0. This is a known kernel bug. We just ignore it."));
+            }
+            else if (r != sizeof(nticks) && errno != EINTR) {
+               barf("Itimer: read(timerfd) failed with %s and returned %zd", strerror(errno), r);
             }
         } else {
             if (usleep(TimeToUS(itimer_interval)) != 0 && errno != EINTR) {
@@ -169,7 +177,7 @@ initTicker (Time interval, TickProc handle_tick)
         pthread_setname_np(thread, "ghc_ticker");
 #endif
     } else {
-        barf("Itimer: Failed to spawn thread");
+        barf("Itimer: Failed to spawn thread: %s", strerror(errno));
     }
 }
 
@@ -203,7 +211,7 @@ exitTicker (bool wait)
     // wait for ticker to terminate if necessary
     if (wait) {
         if (pthread_join(thread, NULL)) {
-            sysErrorBelch("Itimer: Failed to join");
+            sysErrorBelch("Itimer: Failed to join: %s", strerror(errno));
         }
         closeMutex(&mutex);
         closeCondition(&start_cond);



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/aa3fb803cccc0c235dfe8b7c9925d63b73134577...df9671ef7999ad84f1707c8fd54bd236d5d17dac

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/aa3fb803cccc0c235dfe8b7c9925d63b73134577...df9671ef7999ad84f1707c8fd54bd236d5d17dac
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