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>

6 files changed, 177 insertions, 0 deletions

diff --git a/Documentation/perf_counter/Makefile b/Documentation/perf_counter/Makefile
index efb05892db69..51b13f989833 100644
--- a/Documentation/perf_counter/Makefile
+++ b/Documentation/perf_counter/Makefile
@@ -297,11 +297,13 @@ LIB_H += util/util.h
 LIB_H += util/help.h
 LIB_H += util/strbuf.h
 LIB_H += util/run-command.h
+LIB_H += util/sigchain.h
 
 LIB_OBJS += util/abspath.o
 LIB_OBJS += util/alias.o
 LIB_OBJS += util/config.o
 LIB_OBJS += util/ctype.o
+LIB_OBJS += util/environment.o
 LIB_OBJS += util/exec_cmd.o
 LIB_OBJS += util/help.o
 LIB_OBJS += util/levenshtein.o
@@ -314,6 +316,8 @@ LIB_OBJS += util/quote.o
 LIB_OBJS += util/strbuf.o
 LIB_OBJS += util/usage.o
 LIB_OBJS += util/wrapper.o
+LIB_OBJS += util/sigchain.o
+LIB_OBJS += util/pager.o
 
 BUILTIN_OBJS += builtin-help.o
 BUILTIN_OBJS += builtin-record.o
diff --git a/Documentation/perf_counter/builtin-report.c b/Documentation/perf_counter/builtin-report.c
index e2712cd06310..9aef7c54483e 100644
--- a/Documentation/perf_counter/builtin-report.c
+++ b/Documentation/perf_counter/builtin-report.c
@@ -7,6 +7,7 @@
 #include <ctype.h>
 
 #include "util/list.h"
+#include "util/cache.h"
 #include "util/rbtree.h"
 
 #include "perf.h"
@@ -992,5 +993,7 @@ int cmd_report(int argc, const char **argv, const char *prefix)
 
         parse_options(argc, argv, options, report_usage, 0);
 
+        setup_pager();
+
         return __cmd_report();
 }
diff --git a/Documentation/perf_counter/util/environment.c b/Documentation/perf_counter/util/environment.c
new file mode 100644
index 000000000000..9b1c8199e729
--- /dev/null
+++ b/Documentation/perf_counter/util/environment.c
@@ -0,0 +1,8 @@
+/*
+ * We put all the perf config variables in this same object
+ * file, so that programs can link against the config parser
+ * without having to link against all the rest of perf.
+ */
+#include "cache.h"
+
+const char *pager_program;
diff --git a/Documentation/perf_counter/util/pager.c b/Documentation/perf_counter/util/pager.c
new file mode 100644
index 000000000000..a28bccae5458
--- /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;
+}
diff --git a/Documentation/perf_counter/util/sigchain.c b/Documentation/perf_counter/util/sigchain.c
new file mode 100644
index 000000000000..1118b99e57d3
--- /dev/null
+++ b/Documentation/perf_counter/util/sigchain.c
@@ -0,0 +1,52 @@
+#include "sigchain.h"
+#include "cache.h"
+
+#define SIGCHAIN_MAX_SIGNALS 32
+
+struct sigchain_signal {
+        sigchain_fun *old;
+        int n;
+        int alloc;
+};
+static struct sigchain_signal signals[SIGCHAIN_MAX_SIGNALS];
+
+static void check_signum(int sig)
+{
+        if (sig < 1 || sig >= SIGCHAIN_MAX_SIGNALS)
+                die("BUG: signal out of range: %d", sig);
+}
+
+int sigchain_push(int sig, sigchain_fun f)
+{
+        struct sigchain_signal *s = signals + sig;
+        check_signum(sig);
+
+        ALLOC_GROW(s->old, s->n + 1, s->alloc);
+        s->old[s->n] = signal(sig, f);
+        if (s->old[s->n] == SIG_ERR)
+                return -1;
+        s->n++;
+        return 0;
+}
+
+int sigchain_pop(int sig)
+{
+        struct sigchain_signal *s = signals + sig;
+        check_signum(sig);
+        if (s->n < 1)
+                return 0;
+
+        if (signal(sig, s->old[s->n - 1]) == SIG_ERR)
+                return -1;
+        s->n--;
+        return 0;
+}
+
+void sigchain_push_common(sigchain_fun f)
+{
+        sigchain_push(SIGINT, f);
+        sigchain_push(SIGHUP, f);
+        sigchain_push(SIGTERM, f);
+        sigchain_push(SIGQUIT, f);
+        sigchain_push(SIGPIPE, f);
+}
diff --git a/Documentation/perf_counter/util/sigchain.h b/Documentation/perf_counter/util/sigchain.h
new file mode 100644
index 000000000000..618083bce0c6
--- /dev/null
+++ b/Documentation/perf_counter/util/sigchain.h
@@ -0,0 +1,11 @@
+#ifndef SIGCHAIN_H
+#define SIGCHAIN_H
+
+typedef void (*sigchain_fun)(int);
+
+int sigchain_push(int sig, sigchain_fun f);
+int sigchain_pop(int sig);
+
+void sigchain_push_common(sigchain_fun f);
+
+#endif /* SIGCHAIN_H */