Hi, On Wed, May 9, 2018 at 10:01 AM, Lina Iyer <[email protected]> wrote: > +int rpmh_write(const struct device *dev, enum rpmh_state state, > + const struct tcs_cmd *cmd, u32 n) > +{ > + DECLARE_COMPLETION_ONSTACK(compl); > + DEFINE_RPMH_MSG_ONSTACK(dev, state, &compl, rpm_msg); > + int ret; > + > + if (!cmd || !n || n > MAX_RPMH_PAYLOAD) > + return -EINVAL; > + > + memcpy(rpm_msg.cmd, cmd, n * sizeof(*cmd)); > + rpm_msg.msg.num_cmds = n; > + > + ret = __rpmh_write(dev, state, &rpm_msg); > + if (ret) > + return ret; > + > + ret = wait_for_completion_timeout(&compl, RPMH_TIMEOUT_MS);
IMO it's almost never a good idea to use wait_for_completion_timeout() together with a completion that's declared on the stack. If you somehow insist that this is a good idea then I need to see incredibly clear and obvious code/comments that say why it's impossible that the process might somehow try to signal the completion _after_ RPMH_TIMEOUT_MS has expired. Specifically if the timeout happens but the process could still signal a completion later then they will access random data on the stack of a function that has already returned. This causes ridiculously difficult-to-debug crashes. NOTE: You've got timeout set to 10 seconds here. Is that really even useful? IMO just call wait_for_completion() without a timeout. It's much better to have a nice clean hang than a random stack corruption. -Doug
