Fix shutdown with TRACY_NO_EXIT=1 on Android. (#134)

2 files changed, 48 insertions, 9 deletions

diff --git a/extra/systrace/build.sh b/extra/systrace/build.sh
index 8d6b7a8e..1da097a9 100755
--- a/extra/systrace/build.sh
+++ b/extra/systrace/build.sh
@@ -1,4 +1,31 @@
 #!/bin/sh
-clang tracy_systrace.c -s -Os -ffunction-sections -fdata-sections -Wl,--gc-sections -fno-stack-protector -Wl,-z,norelro -Wl,--build-id=none -nostdlib -ldl -o tracy_systrace
-strip --strip-all -R .note.gnu.gold-version -R .comment -R .note -R .note.gnu.build-id -R .note.ABI-tag -R .eh_frame -R .eh_frame_hdr -R .gnu.hash -R .gnu.version -R .got tracy_systrace
-sstrip -z tracy_systrace
+
+# These may be passed as environment variables, or will use the following defaults.
+: ${CC:=clang}
+: ${STRIP:=strip}
+: ${SSTRIP:=sstrip}
+
+if [ ! -x "$(command -v "${CC}")" ]
+then
+  echo "Set the CC environment variable to a C compiler."
+  exit 1
+fi
+
+if [ ! -x "$(command -v "${STRIP}")" ]
+then
+  echo "Set the STRIP environment variable to the strip utility."
+  exit 1
+fi
+
+if [ ! -x "$(command -v "${SSTRIP}")" ]
+then
+  echo "Set the SSTRIP environment variable to the sstrip utility, which can be obtained from https://github.com/BR903/ELFkickers ."
+  exit 1
+fi
+
+$CC tracy_systrace.c -s -Os -ffunction-sections -fdata-sections -Wl,--gc-sections -fno-stack-protector -Wl,-z,norelro -Wl,--build-id=none -nostdlib -ldl -o tracy_systrace
+
+$STRIP --strip-all -R .note.gnu.gold-version -R .comment -R .note -R .note.gnu.build-id -R .note.ABI-tag -R .eh_frame -R .eh_frame_hdr -R .gnu.version -R .got tracy_systrace
+
+$SSTRIP -z tracy_systrace
+
diff --git a/extra/systrace/tracy_systrace.c b/extra/systrace/tracy_systrace.c
index 530f05f5..58fcbfe8 100644
--- a/extra/systrace/tracy_systrace.c
+++ b/extra/systrace/tracy_systrace.c
@@ -33,18 +33,30 @@ void _start()
     int kernelFd = sym_open( "/sys/kernel/debug/tracing/trace_pipe", O_RDONLY );
     if( kernelFd < 0 ) sym_exit( 0 );
 
-    struct pollfd pfd;
-    pfd.fd = kernelFd;
-    pfd.events = POLLIN | POLLERR;
+    struct pollfd pfd_in;
+    pfd_in.fd = kernelFd;
+    pfd_in.events = POLLIN | POLLERR;
+
+    struct pollfd pfd_out;
+    pfd_out.fd = STDOUT_FILENO;
+    pfd_out.events = POLLERR;
 
     struct timespec sleepTime;
     sleepTime.tv_sec = 0;
     sleepTime.tv_nsec = 1000 * 1000 * 10;
 
-    for(;;)
+    // While the pipe is open (no POLLERR on the output fd)
+    while( sym_poll( &pfd_out, 1, 0) <= 0 )
     {
-        while( sym_poll( &pfd, 1, 0 ) <= 0 ) sym_nanosleep( &sleepTime, NULL );
-        const int rd = sym_read( kernelFd, buf, BufSize );
+        // If there is neither data (POLLIN) nor an error (POLLERR) on
+        // the read fd, sleep. This implements a blocking read without relying
+        // on the Linux kernel's implementation of blocking reads which causes
+        // a large number of context switches.
+        if( sym_poll( &pfd_in, 1, 0 ) <= 0 ) {
+            sym_nanosleep( &sleepTime, NULL );
+            continue;  // go back to the while condition polling the output fd
+        }
+        const ssize_t rd = sym_read( kernelFd, buf, BufSize );
         if( rd <= 0 ) break;
         sym_write( STDOUT_FILENO, buf, rd );
     }