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Earlier versions of Tree SRCU were subject to a counter overflow bug that could theoretically result in too-short grace periods. This commit eliminates this problem by adding an update-side memory barrier. The short explanation is that if the updater sums the unlock counts too late to see a given __srcu_read_unlock() increment, that CPU's next __srcu_read_lock() must see the new value of ->srcu_idx, thus incrementing the other bank of counters. This eliminates the possibility of destructive counter overflow as long as the srcu_read_lock() nesting level does not exceed floor(ULONG_MAX/NR_CPUS/2), which should be an eminently reasonable nesting limit, especially on 64-bit systems. Reported-by: Lance Roy <ldr709@gmail.com> Suggested-by: Lance Roy <ldr709@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
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| .. | ||
| Makefile | ||
| rcu_segcblist.c | ||
| rcu_segcblist.h | ||
| rcu.h | ||
| rcuperf.c | ||
| rcutorture.c | ||
| srcu.c | ||
| srcutiny.c | ||
| srcutree.c | ||
| sync.c | ||
| tiny_plugin.h | ||
| tiny.c | ||
| tree_exp.h | ||
| tree_plugin.h | ||
| tree_trace.c | ||
| tree.c | ||
| tree.h | ||
| update.c | ||