diff options
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-03-10 12:55:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-03-10 15:55:11 -0700
commit1b23336ad98b3666c216617227c7767cd60a22be (patch)
parent260219cc48cfb22486e5d0d706c978228a080d63 (diff)
idr: make idr_remove_all() do removal -before- free_layer()
Fix a problem in the IDR system, where an idr_remove_all() hands a data element to call_rcu() (via free_layer()) before making that data element inaccessible to new readers. This is very bad, and results in readers still having a reference to this data element at the end of the grace period. Tests on large machines that concurrently map and unmap user-space memory within the same multithreaded process result in crashes within about five minutes. Applying this patch increases the kernel's longevity to the three-to-eight-hour range. There appear to be other similar problems in idr_get_empty_slot() and sub_remove(), but I fixed the easy one in idr_remove_all() first. It is therefore no surprise that failures still occur. Located-by: Milton Miller II <miltonm@austin.ibm.com> Tested-by: Milton Miller II <miltonm@austin.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Manfred Spraul <manfred@colorfullife.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, 1 insertions, 1 deletions
diff --git a/lib/idr.c b/lib/idr.c
index c11c5765cde..dab4bca86f5 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -449,6 +449,7 @@ void idr_remove_all(struct idr *idp)
n = idp->layers * IDR_BITS;
p = idp->top;
+ rcu_assign_pointer(idp->top, NULL);
max = 1 << n;
id = 0;
@@ -467,7 +468,6 @@ void idr_remove_all(struct idr *idp)
p = *--paa;
- rcu_assign_pointer(idp->top, NULL);
idp->layers = 0;