linux-kernel - [080/117] powerpc: Move checks in pseries_mach_cpu

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Date:	Mon, 10 May 2010 15:32:51 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [080/117] powerpc: Move checks in pseries_mach_cpu_die()

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>

commit 0212f2602a38e740d5a96aba4cebfc2ebc993ecf upstream.

Rearrange condition checks for better code readability and
	prevention of possible race conditions when
	preferred_offline_state can potentially change during the
	execution of pseries_mach_cpu_die().  The patch will make
	pseries_mach_cpu_die() put cpu in one of the consistent states
	and not hit the run over BUG()

Signed-off-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc: Gautham R Shenoy <ego@...ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/powerpc/platforms/pseries/hotplug-cpu.c |   30 +++++++++++++--------------
 1 file changed, 15 insertions(+), 15 deletions(-)

--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -140,25 +140,25 @@ static void pseries_mach_cpu_die(void)
 		if (!get_lppaca()->shared_proc)
 			get_lppaca()->donate_dedicated_cpu = 0;
 		get_lppaca()->idle = 0;
-	}
 
-	if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
-		unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
+		if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
+			unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
 
-		/*
-		 * Call to start_secondary_resume() will not return.
-		 * Kernel stack will be reset and start_secondary()
-		 * will be called to continue the online operation.
-		 */
-		start_secondary_resume();
+			/*
+			 * Call to start_secondary_resume() will not return.
+			 * Kernel stack will be reset and start_secondary()
+			 * will be called to continue the online operation.
+			 */
+			start_secondary_resume();
+		}
+	}
 
-	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
+	/* Requested state is CPU_STATE_OFFLINE at this point */
+	WARN_ON(get_preferred_offline_state(cpu) != CPU_STATE_OFFLINE);
 
-		set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
-		unregister_slb_shadow(hard_smp_processor_id(),
-					__pa(get_slb_shadow()));
-		rtas_stop_self();
-	}
+	set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
+	unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
+	rtas_stop_self();
 
 	/* Should never get here... */
 	BUG();


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