perf_counter tools: Add built-in pager support
Add Git's pager.c (and sigchain) code. A command only
has to call setup_pager() to get paged interactive
output.
Non-interactive (redirected, command-piped, etc.) uses
are not affected.
Update perf-report to make use of this.
[ Impact: new feature ]
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/perf_counter/util/pager.c b/Documentation/perf_counter/util/pager.c
new file mode 100644
index 0000000..a28bcca
--- /dev/null
+++ b/Documentation/perf_counter/util/pager.c
@@ -0,0 +1,99 @@
+#include "cache.h"
+#include "run-command.h"
+#include "sigchain.h"
+
+/*
+ * This is split up from the rest of git so that we can do
+ * something different on Windows.
+ */
+
+static int spawned_pager;
+
+#ifndef __MINGW32__
+static void pager_preexec(void)
+{
+ /*
+ * Work around bug in "less" by not starting it until we
+ * have real input
+ */
+ fd_set in;
+
+ FD_ZERO(&in);
+ FD_SET(0, &in);
+ select(1, &in, NULL, &in, NULL);
+
+ setenv("LESS", "FRSX", 0);
+}
+#endif
+
+static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
+static struct child_process pager_process;
+
+static void wait_for_pager(void)
+{
+ fflush(stdout);
+ fflush(stderr);
+ /* signal EOF to pager */
+ close(1);
+ close(2);
+ finish_command(&pager_process);
+}
+
+static void wait_for_pager_signal(int signo)
+{
+ wait_for_pager();
+ sigchain_pop(signo);
+ raise(signo);
+}
+
+void setup_pager(void)
+{
+ const char *pager = getenv("PERF_PAGER");
+
+ if (!isatty(1))
+ return;
+ if (!pager) {
+ if (!pager_program)
+ perf_config(perf_default_config, NULL);
+ pager = pager_program;
+ }
+ if (!pager)
+ pager = getenv("PAGER");
+ if (!pager)
+ pager = "less";
+ else if (!*pager || !strcmp(pager, "cat"))
+ return;
+
+ spawned_pager = 1; /* means we are emitting to terminal */
+
+ /* spawn the pager */
+ pager_argv[2] = pager;
+ pager_process.argv = pager_argv;
+ pager_process.in = -1;
+#ifndef __MINGW32__
+ pager_process.preexec_cb = pager_preexec;
+#endif
+ if (start_command(&pager_process))
+ return;
+
+ /* original process continues, but writes to the pipe */
+ dup2(pager_process.in, 1);
+ if (isatty(2))
+ dup2(pager_process.in, 2);
+ close(pager_process.in);
+
+ /* this makes sure that the parent terminates after the pager */
+ sigchain_push_common(wait_for_pager_signal);
+ atexit(wait_for_pager);
+}
+
+int pager_in_use(void)
+{
+ const char *env;
+
+ if (spawned_pager)
+ return 1;
+
+ env = getenv("PERF_PAGER_IN_USE");
+ return env ? perf_config_bool("PERF_PAGER_IN_USE", env) : 0;
+}