Fix: mmap write() for large subbuffers and handle EINTR (v2)

[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 2b55fd4637ead2b056fcafecc47ef5504d7c5df5..47c0d460ffb60cc612d9806325602c6eac459023 100644 (file)
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -49,7 +49,7 @@ ssize_t lttng_ustconsumer_on_read_subbuffer_mmap(
                struct lttng_consumer_stream *stream, unsigned long len)
 {
        unsigned long mmap_offset;
-       long ret = 0;
+       long ret = 0, written = 0;
        off_t orig_offset = stream->out_fd_offset;
        int outfd = stream->out_fd;
 
@@ -59,29 +59,39 @@ ssize_t lttng_ustconsumer_on_read_subbuffer_mmap(
        if (ret != 0) {
                errno = -ret;
                PERROR("ustctl_get_mmap_read_offset");
+               written = ret;
                goto end;
        }
        while (len > 0) {
                ret = write(outfd, stream->mmap_base + mmap_offset, len);
-               if (ret >= len) {
-                       len = 0;
-               } else if (ret < 0) {
-                       errno = -ret;
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               /* restart the interrupted system call */
+                               continue;
+                       } else {
+                               PERROR("Error in file write");
+                               if (written == 0) {
+                                       written = ret;
+                               }
+                               goto end;
+                       }
+               } else if (ret > len) {
                        PERROR("Error in file write");
+                       written += ret;
                        goto end;
+               } else {
+                       len -= ret;
+                       mmap_offset += ret;
                }
                /* This won't block, but will start writeout asynchronously */
                lttng_sync_file_range(outfd, stream->out_fd_offset, ret,
                                SYNC_FILE_RANGE_WRITE);
                stream->out_fd_offset += ret;
+               written += ret;
        }
-
        lttng_consumer_sync_trace_file(stream, orig_offset);
-
-       goto end;
-
 end:
-       return ret;
+       return written;
 }
 
 /*
@@ -384,7 +394,7 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
        assert(err == 0);
        /* write the subbuffer to the tracefile */
        ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
-       if (ret < 0) {
+       if (ret != len) {
                /*
                 * display the error but continue processing to try
                 * to release the subbuffer