From c485cdb0249415b8aee5968b2b8854921e152854 Mon Sep 17 00:00:00 2001
From: Ryan Prichard <rprichard@google.com>
Date: Tue, 30 Apr 2019 14:47:34 -0700
Subject: Revert fwalk/sfp locking to fix concurrent reads

The locking can fail in a couple of ways:

 - A concurrent fread from an unbuffered or line-buffered file flushes
   the output of other line-buffered files, and if _fwalk locks every
   file, then the fread blocks until other file reads have completed.

 - __sfp can initialize a file lock while _fwalk is locking/unlocking it.

For now, revert to the behavior Bionic had in previous releases. This
commit reverts the file locking parts of commit
468efc80da2504f4ae7de8b5e137426d44dda9d7.

Bug: http://b/131251441
Bug: http://b/130189834
Test: bionic unit tests
Change-Id: I9e20b9cd8ccd14e7962f7308e174f08af72b56c6
---
 tests/stdio_test.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'tests/stdio_test.cpp')

diff --git a/tests/stdio_test.cpp b/tests/stdio_test.cpp
index 65a942c37..c237d6d32 100644
--- a/tests/stdio_test.cpp
+++ b/tests/stdio_test.cpp
@@ -29,6 +29,7 @@
 #include <locale.h>
 
 #include <string>
+#include <thread>
 #include <vector>
 
 #include <android-base/file.h>
@@ -2577,3 +2578,24 @@ TEST(STDIO_TEST, dev_std_files) {
   ASSERT_LT(0, length);
   ASSERT_EQ("/proc/self/fd/2", std::string(path, length));
 }
+
+TEST(STDIO_TEST, fread_with_locked_file) {
+  // Reading an unbuffered/line-buffered file from one thread shouldn't block on
+  // files locked on other threads, even if it flushes some line-buffered files.
+  FILE* fp1 = fopen("/dev/zero", "r");
+  ASSERT_TRUE(fp1 != nullptr);
+  flockfile(fp1);
+
+  std::thread([] {
+    for (int mode : { _IONBF, _IOLBF }) {
+      FILE* fp2 = fopen("/dev/zero", "r");
+      ASSERT_TRUE(fp2 != nullptr);
+      setvbuf(fp2, nullptr, mode, 0);
+      ASSERT_EQ('\0', fgetc(fp2));
+      fclose(fp2);
+    }
+  }).join();
+
+  funlockfile(fp1);
+  fclose(fp1);
+}
-- 
cgit v1.2.3


From 31c7309dc6d4385f120ec30dae3c0adcb5a7db1d Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Tue, 7 May 2019 10:03:02 -0700
Subject: Add SEEK_DATA and SEEK_HOLE constants.

Without pulling in <linux/fs.h>, the UAPI source of these constants,
because it's full of pollution, in particular a macro called BLOCK_SIZE
that breaks a lot of stuff.

Test: treehugger
Change-Id: I7258ec57e91c67645c2b4d0ce44850d757c4bb12
---
 tests/stdio_test.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'tests/stdio_test.cpp')

diff --git a/tests/stdio_test.cpp b/tests/stdio_test.cpp
index c237d6d32..01b4dbab7 100644
--- a/tests/stdio_test.cpp
+++ b/tests/stdio_test.cpp
@@ -19,6 +19,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <linux/fs.h>
 #include <math.h>
 #include <stdio.h>
 #include <sys/types.h>
@@ -2599,3 +2600,13 @@ TEST(STDIO_TEST, fread_with_locked_file) {
   funlockfile(fp1);
   fclose(fp1);
 }
+
+TEST(STDIO_TEST, SEEK_macros) {
+  ASSERT_EQ(0, SEEK_SET);
+  ASSERT_EQ(1, SEEK_CUR);
+  ASSERT_EQ(2, SEEK_END);
+  ASSERT_EQ(3, SEEK_DATA);
+  ASSERT_EQ(4, SEEK_HOLE);
+  // So we'll notice if Linux grows another constant in <linux/fs.h>...
+  ASSERT_EQ(SEEK_MAX, SEEK_HOLE);
+}
-- 
cgit v1.2.3