From 2b3ebaf5c03acaffa1607d6385a2508f4bdd320e Mon Sep 17 00:00:00 2001
From: Tom Cherry <tomcherry@google.com>
Date: Fri, 31 Jul 2020 15:21:54 -0700
Subject: [PATCH] SocketClient: don't ignore SIGPIPE

1) All current users are better off ignoring SIGPIPE at the beginning
   of their process instead of ignoring it just for SocketClient
2) This isn't thread safe if users did want it, since sigaction()
   ignores SIGPIPE for the entire process
3) This costs 5-10% of logd CPU time when logcat is reading logs

Also clean up the error handling in SocketClient::sendDataLockedv().

Test: kill logcat and see that logd doesn't crash
Test: run simpleperf and see that no cycles are going to sigaction
Change-Id: I6532c8a0d71338e534411707b9a9bd785145c730
---
 libsysutils/src/SocketClient.cpp | 51 ++++++++++----------------------
 logd/main.cpp                    |  2 ++
 2 files changed, 18 insertions(+), 35 deletions(-)

diff --git a/libsysutils/src/SocketClient.cpp b/libsysutils/src/SocketClient.cpp
index fe2f3d668..e90afcd18 100644
--- a/libsysutils/src/SocketClient.cpp
+++ b/libsysutils/src/SocketClient.cpp
@@ -201,50 +201,31 @@ int SocketClient::sendDataLockedv(struct iovec *iov, int iovcnt) {
         return 0;
     }
 
-    int ret = 0;
-    int e = 0; // SLOGW and sigaction are not inert regarding errno
     int current = 0;
 
-    struct sigaction new_action, old_action;
-    memset(&new_action, 0, sizeof(new_action));
-    new_action.sa_handler = SIG_IGN;
-    sigaction(SIGPIPE, &new_action, &old_action);
-
     for (;;) {
-        ssize_t rc = TEMP_FAILURE_RETRY(
-            writev(mSocket, iov + current, iovcnt - current));
-
-        if (rc > 0) {
-            size_t written = rc;
-            while ((current < iovcnt) && (written >= iov[current].iov_len)) {
-                written -= iov[current].iov_len;
-                current++;
-            }
-            if (current == iovcnt) {
-                break;
-            }
-            iov[current].iov_base = (char *)iov[current].iov_base + written;
-            iov[current].iov_len -= written;
-            continue;
-        }
+        ssize_t rc = TEMP_FAILURE_RETRY(writev(mSocket, iov + current, iovcnt - current));
 
         if (rc == 0) {
-            e = EIO;
+            errno = EIO;
             SLOGW("0 length write :(");
-        } else {
-            e = errno;
-            SLOGW("write error (%s)", strerror(e));
+            return -1;
+        } else if (rc < 0) {
+            SLOGW("write error (%s)", strerror(errno));
+            return -1;
         }
-        ret = -1;
-        break;
-    }
 
-    sigaction(SIGPIPE, &old_action, &new_action);
-
-    if (e != 0) {
-        errno = e;
+        size_t written = rc;
+        while (current < iovcnt && written >= iov[current].iov_len) {
+            written -= iov[current].iov_len;
+            current++;
+        }
+        if (current == iovcnt) {
+            return 0;
+        }
+        iov[current].iov_base = (char*)iov[current].iov_base + written;
+        iov[current].iov_len -= written;
     }
-    return ret;
 }
 
 void SocketClient::incRef() {
diff --git a/logd/main.cpp b/logd/main.cpp
index 93dadf597..c92c5b719 100644
--- a/logd/main.cpp
+++ b/logd/main.cpp
@@ -218,6 +218,8 @@ static int issueReinit() {
 // logging plugins like auditd and restart control. Additional
 // transitory per-client threads are created for each reader.
 int main(int argc, char* argv[]) {
+    // We want EPIPE when a reader disconnects, not to terminate logd.
+    signal(SIGPIPE, SIG_IGN);
     // logd is written under the assumption that the timezone is UTC.
     // If TZ is not set, persist.sys.timezone is looked up in some time utility
     // libc functions, including mktime. It confuses the logd time handling,