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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2009-03-10 12:55:52 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-03-10 15:55:11 -0700 |
| commit | 1b23336ad98b3666c216617227c7767cd60a22be (patch) | |
| tree | 8743554370742f55d993bfd6b5a281f81bc4dd0b /lib/idr.c | |
| parent | 260219cc48cfb22486e5d0d706c978228a080d63 (diff) | |
| download | linux-3.10-1b23336ad98b3666c216617227c7767cd60a22be.tar.gz linux-3.10-1b23336ad98b3666c216617227c7767cd60a22be.tar.bz2 linux-3.10-1b23336ad98b3666c216617227c7767cd60a22be.zip | |
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>
Diffstat (limited to 'lib/idr.c')
| -rw-r--r-- | lib/idr.c | 2 |
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; } EXPORT_SYMBOL(idr_remove_all); |