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>

1 files changed, 52 insertions, 0 deletions

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);
+}