Make the taint flags reliable

It's somewhat unlikely that it happens, but right now a race window
between interrupts or machine checks or oopses could corrupt the tainted
bitmap because it is modified in a non atomic fashion.

Convert the taint variable to an unsigned long and use only atomic bit
operations on it.

Unfortunately this means the intvec sysctl functions cannot be used on it
anymore.

It turned out the taint sysctl handler could actually be simplified a bit
(since it only increases capabilities) so this patch actually removes
code.

[akpm@linux-foundation.org: remove unneeded include]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 7 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 8c3aca7cb343..7ed9e070a6e9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -282,6 +282,8 @@ static void __cpuinit smp_callin(void)
         cpu_set(cpuid, cpu_callin_map);
 }
 
+static int __cpuinitdata unsafe_smp;
+
 /*
  * Activate a secondary processor.
  */
@@ -397,7 +399,7 @@ static void __cpuinit smp_apply_quirks(struct cpuinfo_x86 *c)
                                 goto valid_k7;
 
                 /* If we get here, not a certified SMP capable AMD system. */
-                add_taint(TAINT_UNSAFE_SMP);
+                unsafe_smp = 1;
         }
 
 valid_k7:
@@ -414,12 +416,10 @@ static void __cpuinit smp_checks(void)
          * Don't taint if we are running SMP kernel on a single non-MP
          * approved Athlon
          */
-        if (tainted & TAINT_UNSAFE_SMP) {
-                if (num_online_cpus())
-                        printk(KERN_INFO "WARNING: This combination of AMD"
-                                "processors is not suitable for SMP.\n");
-                else
-                        tainted &= ~TAINT_UNSAFE_SMP;
+        if (unsafe_smp && num_online_cpus() > 1) {
+                printk(KERN_INFO "WARNING: This combination of AMD"
+                        "processors is not suitable for SMP.\n");
+                add_taint(TAINT_UNSAFE_SMP);
         }
 }