From bb9bd24d034e8ff92545294f7ca12c415e0af52e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 5 Mar 2010 15:03:25 -0800 Subject: [PATCH] --- yaml --- r: 187888 b: refs/heads/master c: 3f379b03fbfddd20536389a85c6456f8233d1f8d h: refs/heads/master v: v3 --- [refs] | 2 +- trunk/kernel/trace/ftrace.c | 22 +++++++++++++--------- 2 files changed, 14 insertions(+), 10 deletions(-) diff --git a/[refs] b/[refs] index eb564ecfabd2..a5da8b3c1e7a 100644 --- a/[refs] +++ b/[refs] @@ -1,2 +1,2 @@ --- -refs/heads/master: 54dbf96c921513bf98484a20ef366d51944a4c4d +refs/heads/master: 3f379b03fbfddd20536389a85c6456f8233d1f8d diff --git a/trunk/kernel/trace/ftrace.c b/trunk/kernel/trace/ftrace.c index 83783579378f..8c5adc0e5db3 100644 --- a/trunk/kernel/trace/ftrace.c +++ b/trunk/kernel/trace/ftrace.c @@ -27,6 +27,7 @@ #include #include #include +#include #include @@ -88,18 +89,22 @@ ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub; static int ftrace_set_func(unsigned long *array, int *idx, char *buffer); #endif +/* + * Traverse the ftrace_list, invoking all entries. The reason that we + * can use rcu_dereference_raw() is that elements removed from this list + * are simply leaked, so there is no need to interact with a grace-period + * mechanism. The rcu_dereference_raw() calls are needed to handle + * concurrent insertions into the ftrace_list. + * + * Silly Alpha and silly pointer-speculation compiler optimizations! + */ static void ftrace_list_func(unsigned long ip, unsigned long parent_ip) { - struct ftrace_ops *op = ftrace_list; - - /* in case someone actually ports this to alpha! */ - read_barrier_depends(); + struct ftrace_ops *op = rcu_dereference_raw(ftrace_list); /*see above*/ while (op != &ftrace_list_end) { - /* silly alpha */ - read_barrier_depends(); op->func(ip, parent_ip); - op = op->next; + op = rcu_dereference_raw(op->next); /*see above*/ }; } @@ -154,8 +159,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops) * the ops->next pointer is valid before another CPU sees * the ops pointer included into the ftrace_list. */ - smp_wmb(); - ftrace_list = ops; + rcu_assign_pointer(ftrace_list, ops); if (ftrace_enabled) { ftrace_func_t func;