diff options
| -rw-r--r-- | usr/src/cmd/cpc/common/cpustat.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/usr/src/cmd/cpc/common/cpustat.c b/usr/src/cmd/cpc/common/cpustat.c index 965fbadfea..79daedc50b 100644 --- a/usr/src/cmd/cpc/common/cpustat.c +++ b/usr/src/cmd/cpc/common/cpustat.c @@ -23,6 +23,10 @@ * Use is subject to license terms. */ +/* + * Copyright 2018 Joyent, Inc. + */ + #include <sys/types.h> #include <sys/processor.h> #include <sys/pset.h> @@ -289,6 +293,21 @@ main(int argc, char *argv[]) (void) setvbuf(stdout, NULL, _IOLBF, 0); /* + * By design, cpustat (regrettably) has multiple threads racing in + * write(2) to generate output. As there are no guarantees made with + * respect to the atomicity of concurrent writes on non-O_APPEND file + * descriptors, we must set O_APPEND on stdout to assure that no output + * is lost. If cpustat is rearchitected such that only one thread is + * generating output (which would also assure that the output is always + * in a consistent order), this code should be removed. + */ + if (fcntl(1, F_SETFL, fcntl(1, F_GETFL) | O_APPEND) == -1) { + (void) fprintf(stderr, gettext("%s: cannot set output to be " + "append-only - %s\n"), opts->pgmname, strerror(errno)); + return (1); + } + + /* * If no system-mode only sets were created, no soaker threads will be * needed. */ |