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authorIngo Molnar <mingo@elte.hu>2007-11-07 18:37:48 +0100
committerThomas Gleixner <tglx@apollo.(none)>2007-11-17 16:27:00 +0100
commit4307d1e5ada595c87f9a4d16db16ba5edb70dcb1 (patch)
treebae1a90cc162a0d5bd1a78290ffb1f445fc07d80 /kernel/sys.c
parentx86: voyager use correct header file name (diff)
downloadlinux-4307d1e5ada595c87f9a4d16db16ba5edb70dcb1.tar.xz
linux-4307d1e5ada595c87f9a4d16db16ba5edb70dcb1.zip
x86: ignore the sys_getcpu() tcache parameter
dont use the vgetcpu tcache - it's causing problems with tasks migrating, they'll see the old cache up to a jiffy after the migration, further increasing the costs of the migration. In the worst case they see a complete bogus information from the tcache, when a sys_getcpu() call "invalidated" the cache info by incrementing the jiffies _and_ the cpuid info in the cache and the following vdso_getcpu() call happens after vdso_jiffies have been incremented. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/sys.c')
-rw-r--r--kernel/sys.c20
1 files changed, 1 insertions, 19 deletions
diff --git a/kernel/sys.c b/kernel/sys.c
index 304b5410d746..d1fe71eb4546 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1750,7 +1750,7 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
}
asmlinkage long sys_getcpu(unsigned __user *cpup, unsigned __user *nodep,
- struct getcpu_cache __user *cache)
+ struct getcpu_cache __user *unused)
{
int err = 0;
int cpu = raw_smp_processor_id();
@@ -1758,24 +1758,6 @@ asmlinkage long sys_getcpu(unsigned __user *cpup, unsigned __user *nodep,
err |= put_user(cpu, cpup);
if (nodep)
err |= put_user(cpu_to_node(cpu), nodep);
- if (cache) {
- /*
- * The cache is not needed for this implementation,
- * but make sure user programs pass something
- * valid. vsyscall implementations can instead make
- * good use of the cache. Only use t0 and t1 because
- * these are available in both 32bit and 64bit ABI (no
- * need for a compat_getcpu). 32bit has enough
- * padding
- */
- unsigned long t0, t1;
- get_user(t0, &cache->blob[0]);
- get_user(t1, &cache->blob[1]);
- t0++;
- t1++;
- put_user(t0, &cache->blob[0]);
- put_user(t1, &cache->blob[1]);
- }
return err ? -EFAULT : 0;
}