kernel: add missing symbol

Enabling KERNEL_FTRACE exposes the HIST_TRIGGERS triggers symbol. Add a
build option for it to fix build failures with KERNEL_FTRACE enabled.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index e993dc0d8cc764bae63ba5025f3b72c9c563dc71..8ebe1b7070a73775f7938d5e8ec7a00a9045f821 100644 (file)
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -349,6 +349,19 @@ config KERNEL_PREEMPT_TRACER
          enabled. This option and the irqs-off timing option can be
          used together or separately.)
 
+config KERNEL_HIST_TRIGGERS
+       bool "Histogram triggers"
+       depends on KERNEL_FTRACE
+       help
+         Hist triggers allow one or more arbitrary trace event fields to be
+         aggregated into hash tables and dumped to stdout by reading a
+         debugfs/tracefs file. They're useful for gathering quick and dirty
+         (though precise) summaries of event activity as an initial guide for
+         further investigation using more advanced tools.
+
+         Inter-event tracing of quantities such as latencies is also
+         supported using hist triggers under this option.
+
 config KERNEL_DEBUG_KERNEL
        bool
        default n