linux-kernel - [patch] x86, bts: use atomic memory allocation

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Date:	Wed, 18 Mar 2009 19:27:00 +0100
From:	Markus Metzger <markus.t.metzger@...el.com>
To:	linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...utronix.de,
	hpa@...or.com
Cc:	markus.t.metzger@...el.com, markus.t.metzger@...il.com,
	roland@...hat.com, eranian@...glemail.com, oleg@...hat.com,
	juan.villacis@...el.com, ak@...ux.jf.intel.com
Subject: [patch] x86, bts: use atomic memory allocation

Ds_request_bts() needs to allocate memory. It uses GFP_KERNEL.

Hw-branch-tracer calls ds_request_bts() within on_each_cpu().

Use atomic memory allocation to allow it to be used in that context.


Signed-off-by: Markus Metzger <markus.t.metzger@...el.com>
---

Index: git-tip/arch/x86/kernel/ds.c
===================================================================
--- git-tip.orig/arch/x86/kernel/ds.c	2009-03-17 12:26:07.000000000 +0100
+++ git-tip/arch/x86/kernel/ds.c	2009-03-17 13:30:09.000000000 +0100
@@ -255,8 +255,13 @@ static inline struct ds_context *ds_get_
 	struct ds_context *new_context = NULL;
 	unsigned long irq;
 
-	/* Chances are small that we already have a context. */
-	new_context = kzalloc(sizeof(*new_context), GFP_KERNEL);
+	/*
+	 * Chances are small that we already have a context.
+	 *
+	 * Contexts for per-cpu tracing are allocated using
+	 * smp_call_function(). We must not sleep.
+	 */
+	new_context = kzalloc(sizeof(*new_context), GFP_ATOMIC);
 	if (!new_context)
 		return NULL;
 
@@ -662,8 +667,12 @@ struct bts_tracer *ds_request_bts(struct
 	if (ovfl)
 		goto out;
 
+	/*
+	 * Per-cpu tracing is typically requested using smp_call_function().
+	 * We must not sleep.
+	 */
 	error = -ENOMEM;
-	tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
+	tracer = kzalloc(sizeof(*tracer), GFP_ATOMIC);
 	if (!tracer)
 		goto out;
 	tracer->ovfl = ovfl;
@@ -722,8 +731,12 @@ struct pebs_tracer *ds_request_pebs(stru
 	if (ovfl)
 		goto out;
 
+	/*
+	 * Per-cpu tracing is typically requested using smp_call_function().
+	 * We must not sleep.
+	 */
 	error = -ENOMEM;
-	tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
+	tracer = kzalloc(sizeof(*tracer), GFP_ATOMIC);
 	if (!tracer)
 		goto out;
 	tracer->ovfl = ovfl;
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