llkd: llkSplit should prevent empty entries

Android Properties

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Android Properties llkd respond to (<prop>_ms parms are in milliseconds):

Android Properties llkd respond to (*prop*_ms parms are in milliseconds):

#### ro.config.low_ram

default false, if true do not sysrq t (dump all threads).

#### ro.llk.blacklist.process

default 0,1,2 (kernel, init and [kthreadd]) plus process names

init,[kthreadd],[khungtaskd],lmkd,lmkd.llkd,llkd,watchdogd,

[watchdogd],[watchdogd/0],...,[watchdogd/<get_nprocs-1>].

[watchdogd],[watchdogd/0],...,[watchdogd/***get_nprocs**-1*].

The string false is the equivalent to an empty list.

Do not watch these processes.  A process can be comm, cmdline or pid reference.

NB: automated default here can be larger than the current maximum property

size of 92.

NB: false is a very very very unlikely process to want to blacklist.

#### ro.llk.blacklist.parent

default 0,2 (kernel and [kthreadd]).

The string false is the equivalent to an empty list.

Do not watch processes that have this parent.

A parent process can be comm, cmdline or pid reference.

#### ro.llk.blacklist.uid

default <empty>, comma separated list of uid numbers or names.

default *empty* or false, comma separated list of uid numbers or names.

The string false is the equivalent to an empty list.

Do not watch processes that match this uid.

Architectural Concerns

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- built-in [khungtask] daemon is too generic and trips on driver code that

  sits around in D state too much.  To switch to S instead makes the task(s)

  killable, so the drivers should be able to resurrect them if needed.

- Properties are limited to 92 characters.

- Create kernel module and associated gTest to actually test panic.

- Create gTest to test out blacklist (ro.llk.blacklist.<properties> generally

- Create gTest to test out blacklist (ro.llk.blacklist.*properties* generally

  not be inputs).  Could require more test-only interfaces to libllkd.

- Speed up gTest using something else than ro.llk.<properties>, which should

  not be inputs.

- Speed up gTest using something else than ro.llk.*properties*, which should

  not be inputs as they should be baked into the product.

          schedUpdate(0),

          nrSwitches(0),

          update(llkUpdate),

          count(0),

          count(0ms),

          pid(pid),

          ppid(ppid),

          uid(-1),

// We only officially support comma separators, but wetware being what they

// are will take some liberty and I do not believe they should be punished.

std::unordered_set<std::string> llkSplit(const std::string& s,

                                         const std::string& delimiters = ", \t:") {

std::unordered_set<std::string> llkSplit(const std::string& s) {

    std::unordered_set<std::string> result;

    // Special case, allow boolean false to empty the list, otherwise expected

    // source of input from android::base::GetProperty will supply the default

    // value on empty content in the property.

    if (s == "false") return result;

    size_t base = 0;

    size_t found;

    while (true) {

        found = s.find_first_of(delimiters, base);

        result.emplace(s.substr(base, found - base));

    while (s.size() > base) {

        auto found = s.find_first_of(", \t:", base);

        // Only emplace content, empty entries are not an option

        if (found != base) result.emplace(s.substr(base, found - base));

        if (found == s.npos) break;

        base = found + 1;

    }