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    Subject[PATCH 5.4 138/309] tracing: Annotate ftrace_graph_notrace_hash pointer with __rcu
    Date
    From: Amol Grover <frextrite@gmail.com>

    [ Upstream commit fd0e6852c407dd9aefc594f54ddcc21d84803d3b ]

    Fix following instances of sparse error
    kernel/trace/ftrace.c:5667:29: error: incompatible types in comparison
    kernel/trace/ftrace.c:5813:21: error: incompatible types in comparison
    kernel/trace/ftrace.c:5868:36: error: incompatible types in comparison
    kernel/trace/ftrace.c:5870:25: error: incompatible types in comparison

    Use rcu_dereference_protected to dereference the newly annotated pointer.

    Link: http://lkml.kernel.org/r/20200205055701.30195-1-frextrite@gmail.com

    Signed-off-by: Amol Grover <frextrite@gmail.com>
    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/trace/ftrace.c | 2 +-
    kernel/trace/trace.h | 8 ++++++--
    2 files changed, 7 insertions(+), 3 deletions(-)

    diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
    index b38c6af10da5b..d297a8bdc681a 100644
    --- a/kernel/trace/ftrace.c
    +++ b/kernel/trace/ftrace.c
    @@ -5103,7 +5103,7 @@ static const struct file_operations ftrace_notrace_fops = {
    static DEFINE_MUTEX(graph_lock);

    struct ftrace_hash __rcu *ftrace_graph_hash = EMPTY_HASH;
    -struct ftrace_hash *ftrace_graph_notrace_hash = EMPTY_HASH;
    +struct ftrace_hash __rcu *ftrace_graph_notrace_hash = EMPTY_HASH;

    enum graph_filter_type {
    GRAPH_FILTER_NOTRACE = 0,
    diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
    index f8fb3786af72a..c4fd5731d6b37 100644
    --- a/kernel/trace/trace.h
    +++ b/kernel/trace/trace.h
    @@ -933,7 +933,7 @@ extern void __trace_graph_return(struct trace_array *tr,

    #ifdef CONFIG_DYNAMIC_FTRACE
    extern struct ftrace_hash __rcu *ftrace_graph_hash;
    -extern struct ftrace_hash *ftrace_graph_notrace_hash;
    +extern struct ftrace_hash __rcu *ftrace_graph_notrace_hash;

    static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
    {
    @@ -986,10 +986,14 @@ static inline void ftrace_graph_addr_finish(struct ftrace_graph_ret *trace)
    static inline int ftrace_graph_notrace_addr(unsigned long addr)
    {
    int ret = 0;
    + struct ftrace_hash *notrace_hash;

    preempt_disable_notrace();

    - if (ftrace_lookup_ip(ftrace_graph_notrace_hash, addr))
    + notrace_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
    + !preemptible());
    +
    + if (ftrace_lookup_ip(notrace_hash, addr))
    ret = 1;

    preempt_enable_notrace();
    --
    2.20.1


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