diff options
| author | Ingo Molnar <mingo@elte.hu> | 2007-11-07 18:37:48 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@apollo.(none)> | 2007-11-17 16:27:00 +0100 |
| commit | 4307d1e5ada595c87f9a4d16db16ba5edb70dcb1 (patch) | |
| tree | bae1a90cc162a0d5bd1a78290ffb1f445fc07d80 /kernel | |
| parent | 434b3d3209a8d8dcda63c3b14815659f4671b0a8 (diff) | |
| download | lwn-4307d1e5ada595c87f9a4d16db16ba5edb70dcb1.tar.gz lwn-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')
| -rw-r--r-- | kernel/sys.c | 20 |
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; } |