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Steven Rostedt (VMware) authored
Naresh reported a bug that appears to be a side effect of the static calls. It happens when going from more than one tracepoint callback to a single one, and removing the first callback on the list. The list of tracepoint callbacks holds data and a function to call with the parameters of that tracepoint and a handler to the associated data. old_list: 0: func = foo; data = NULL; 1: func = bar; data = &bar_struct; new_list: 0: func = bar; data = &bar_struct; CPU 0 CPU 1 ----- ----- tp_funcs = old_list; tp_static_caller = tp_interator __DO_TRACE() data = tp_funcs[0].data = NULL; tp_funcs = new_list; tracepoint_update_call() tp_static_caller = tp_funcs[0] = bar; tp_static_caller(data) bar(data) x = data->item = NULL->item BOOM! To solve this, add a tracepoint_synchronize_unregister() between changing tp_funcs and updating the static tracepoint, that does both a synchronize_rcu() and synchronize_srcu(). This will ensure that when the static call is updated to the single callback that it will be receiving the data that it registered with. Fixes: d25e37d8 ("tracepoint: Optimize using static_call()") Reported-by:
Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/linux-next/CA+G9fYvPXVRO0NV7yL=FxCmFEMYkCwdz7R=9W+_votpT824YJA@mail.gmail.com
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