debuggerd: simplify output handling
Just noticed some opportunities while skimming.
Test: adb shell debuggerd $(adb shell pidof com.android.systemui)
Test: All unit tests pass (both 32 bit and 64 bit).
Test: Ran unit tests in a loop hundreds of times.
Change-Id: I428d0cf599ed603a21944b084b95594db893cbd5
diff --git a/debuggerd/client/debuggerd_client.cpp b/debuggerd/client/debuggerd_client.cpp
index c9e097e..bd1e91d 100644
--- a/debuggerd/client/debuggerd_client.cpp
+++ b/debuggerd/client/debuggerd_client.cpp
@@ -276,6 +276,13 @@
return false;
}
+ // WARNING: It's not possible to replace the below with a splice call.
+ // Due to the way debuggerd does many small writes across the pipe,
+ // this would cause splice to copy a page for each write. The second
+ // pipe fills up based on the number of pages being copied, even
+ // though there is not much data being transferred per page. When
+ // the second pipe is full, everything stops since there is nothing
+ // reading the second pipe to clear it.
char buf[1024];
rc = TEMP_FAILURE_RETRY(read(pipe_read.get(), buf, sizeof(buf)));
if (rc == 0) {
diff --git a/debuggerd/debuggerd.cpp b/debuggerd/debuggerd.cpp
index e20e8d9..26726cf 100644
--- a/debuggerd/debuggerd.cpp
+++ b/debuggerd/debuggerd.cpp
@@ -41,22 +41,6 @@
_exit(exit_code);
}
-static std::thread spawn_redirect_thread(unique_fd fd) {
- return std::thread([fd{ std::move(fd) }]() {
- while (true) {
- char buf[BUFSIZ];
- ssize_t rc = TEMP_FAILURE_RETRY(read(fd.get(), buf, sizeof(buf)));
- if (rc <= 0) {
- return;
- }
-
- if (!android::base::WriteFully(STDOUT_FILENO, buf, rc)) {
- return;
- }
- }
- });
-}
-
int main(int argc, char* argv[]) {
if (argc <= 1) usage(0);
if (argc > 3) usage(1);
@@ -107,14 +91,11 @@
}
}
- unique_fd piperead, pipewrite;
- if (!Pipe(&piperead, &pipewrite)) {
- err(1, "failed to create pipe");
+ unique_fd output_fd(fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 0));
+ if (output_fd.get() == -1) {
+ err(1, "failed to fcntl dup stdout");
}
-
- std::thread redirect_thread = spawn_redirect_thread(std::move(piperead));
- if (!debuggerd_trigger_dump(proc_info.pid, dump_type, 0, std::move(pipewrite))) {
- redirect_thread.join();
+ if (!debuggerd_trigger_dump(proc_info.pid, dump_type, 0, std::move(output_fd))) {
if (pid == proc_info.pid) {
errx(1, "failed to dump process %d", pid);
} else {
@@ -122,6 +103,5 @@
}
}
- redirect_thread.join();
return 0;
}