scripts/gdb: add class to iterate over CPU masks

Will be used first to count module references.  It is optimized to read
the mask only once per stop.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/gdb/linux/cpus.py

@@ -50,6 +50,60 @@ def per_cpu(var_ptr, cpu):
     return pointer.cast(var_ptr.type).dereference()
 
 
+cpu_mask = {}
+
+
+def cpu_mask_invalidate(event):
+    global cpu_mask
+    cpu_mask = {}
+    gdb.events.stop.disconnect(cpu_mask_invalidate)
+    if hasattr(gdb.events, 'new_objfile'):
+        gdb.events.new_objfile.disconnect(cpu_mask_invalidate)
+
+
+class CpuList():
+    def __init__(self, mask_name):
+        global cpu_mask
+        self.mask = None
+        if mask_name in cpu_mask:
+            self.mask = cpu_mask[mask_name]
+        if self.mask is None:
+            self.mask = gdb.parse_and_eval(mask_name + ".bits")
+            if hasattr(gdb, 'events'):
+                cpu_mask[mask_name] = self.mask
+                gdb.events.stop.connect(cpu_mask_invalidate)
+                if hasattr(gdb.events, 'new_objfile'):
+                    gdb.events.new_objfile.connect(cpu_mask_invalidate)
+        self.bits_per_entry = self.mask[0].type.sizeof * 8
+        self.num_entries = self.mask.type.sizeof * 8 / self.bits_per_entry
+        self.entry = -1
+        self.bits = 0
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        while self.bits == 0:
+            self.entry += 1
+            if self.entry == self.num_entries:
+                raise StopIteration
+            self.bits = self.mask[self.entry]
+            if self.bits != 0:
+                self.bit = 0
+                break
+
+        while self.bits & 1 == 0:
+            self.bits >>= 1
+            self.bit += 1
+
+        cpu = self.entry * self.bits_per_entry + self.bit
+
+        self.bits >>= 1
+        self.bit += 1
+
+        return cpu
+
+
 class PerCpu(gdb.Function):
     """Return per-cpu variable.