linux-kernel - PATCH? process_32.c:__switch_to() calls __math_state_restore() before updating current

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Message-ID: <20100204165105.GA5905@redhat.com>
Date:	Thu, 4 Feb 2010 17:51:05 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	linux-kernel@...r.kernel.org
Subject: PATCH? process_32.c:__switch_to() calls __math_state_restore()
	before updating current_task

I didn't try to verify __switch_to()->__math_state_restore() is really
wrong, this is more the question than the patch. But at least the code
looks wrong, it calls __math_state_restore() which uses curent before
current_task was updated.

Uncompiled/untested.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>

--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -377,9 +377,6 @@ __switch_to(struct task_struct *prev_p, 
 	 */
 	arch_end_context_switch(next_p);
 
-	if (preload_fpu)
-		__math_state_restore();
-
 	/*
 	 * Restore %gs if needed (which is common)
 	 */
@@ -388,6 +385,9 @@ __switch_to(struct task_struct *prev_p, 
 
 	percpu_write(current_task, next_p);
 
+	if (preload_fpu)
+		__math_state_restore();
+
 	return prev_p;
 }
 

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