[Xen-devel] [Patch] Add comments of code restrictions inside play_dead()

[Haitao Shan <maillists.shan@xxxxxxxxx>]

This patch adds comments inside play_dead. This can be served as a notice

to developers who will add code to this code path.

Signed-off-by: Shan Haitao <haitao.shan@xxxxxxxxx>

diff -r c5d121fd35c0 xen/arch/x86/domain.c

--- a/xen/arch/x86/domain.c Mon Feb 28 16:55:20 2011 +0000

+++ b/xen/arch/x86/domain.c Tue Mar 01 16:03:40 2011 +0800

@@ -99,6 +99,14 @@ static void default_dead_idle(void)

 

 static void play_dead(void)

 {

+    /*

+     * Important note:

+     *   After cpu_exit_clear, one can never assume per cpu variables are

+     * still accessable. Otherwise, #PF will happen. For example, calling to

+     * printk() will involve tasklet scheduling ,which also touches per cpu

+     * variables.

+     * Consider more carefully when adding code to this path.

+     */

     cpu_exit_clear(smp_processor_id());

     mb();

     local_irq_disable();

Attachment: add_warning_comment_for_play_dead.patch
Description: Binary data

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