Commit 1b23336ad98b3666c216617227c7767cd60a22be
Committed by
Linus Torvalds
1 parent
260219cc48
Exists in
master
and in
20 other branches
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>
Showing 1 changed file with 1 additions and 1 deletions Side-by-side Diff
lib/idr.c
... | ... | @@ -449,6 +449,7 @@ |
449 | 449 | |
450 | 450 | n = idp->layers * IDR_BITS; |
451 | 451 | p = idp->top; |
452 | + rcu_assign_pointer(idp->top, NULL); | |
452 | 453 | max = 1 << n; |
453 | 454 | |
454 | 455 | id = 0; |
... | ... | @@ -467,7 +468,6 @@ |
467 | 468 | p = *--paa; |
468 | 469 | } |
469 | 470 | } |
470 | - rcu_assign_pointer(idp->top, NULL); | |
471 | 471 | idp->layers = 0; |
472 | 472 | } |
473 | 473 | EXPORT_SYMBOL(idr_remove_all); |