linux-kernel - [PATCH v5 18/20] scripts/gdb: Add helper to iterate over CPU masks

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Date:	Tue, 29 Jan 2013 13:38:01 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc:	Jason Wessel <jason.wessel@...driver.com>,
	kgdb-bugreport@...ts.sourceforge.net,
	Andi Kleen <andi@...stfloor.org>,
	Tom Tromey <tromey@...hat.com>,
	Ben Widawsky <ben@...dawsk.net>, Borislav Petkov <bp@...en8.de>
Subject: [PATCH v5 18/20] scripts/gdb: Add helper to iterate over CPU masks

Will be used first to count module references. It is optimized to read
the mask only once per stop and to minimize the loop lengths.

Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
 scripts/gdb/percpu.py |   33 +++++++++++++++++++++++++++++++++
 1 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/scripts/gdb/percpu.py b/scripts/gdb/percpu.py
index 4dab8d3..bc04188 100644
--- a/scripts/gdb/percpu.py
+++ b/scripts/gdb/percpu.py
@@ -43,6 +43,39 @@ def per_cpu(var_ptr, cpu):
 	pointer = var_ptr.cast(get_long_type()) + offset
 	return pointer.cast(var_ptr.type).dereference()
 
+cpu_mask = { }
+
+def for_each_cpu(mask_name, func, arg = None):
+	def invalidate_handler(event):
+		global cpu_online_mask
+		cpu_mask = { }
+		gdb.events.stop.disconnect(invalidate_handler)
+		gdb.events.new_objfile.disconnect(invalidate_handler)
+
+	global cpu_mask
+	mask = None
+	if mask_name in cpu_mask:
+		mask = cpu_mask[mask_name]
+	if mask == None:
+		mask = gdb.parse_and_eval(mask_name + ".bits")
+		cpu_mask[mask_name] = mask
+		gdb.events.stop.connect(invalidate_handler)
+		gdb.events.new_objfile.connect(invalidate_handler)
+
+	max_cpu_id = mask.type.sizeof * 8
+	bits_per_entry = mask[0].type.sizeof * 8
+	for entry in range(max_cpu_id / bits_per_entry):
+		bits = mask[entry]
+		if bits == 0:
+			continue
+		for bit in range(bits_per_entry):
+			if bits & 1:
+				cpu = entry * bits_per_entry + bit
+				func(cpu, arg)
+			bits >>= 1
+			if bits == 0:
+				break
+
 
 class PerCpu(gdb.Function):
 	__doc__ = "Return per-cpu variable.\n" \
-- 
1.7.3.4

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