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Fix potential deadlock in Validator sites:

Browse Source 
There are two mutexes in ValidatorSite: `site_mutex_` and `state_mutex_`. Some
function end up locking both mutexes. However, depending on the call, the
mutexes could be locked in different orders, resulting in deadlocks.

If both mutexes are locked, this patch always locks the `sites_mutex_` first.
This commit is contained in:
seelabs
2021-08-05 20:43:20 -04:00
committed by Nik Bougalis
parent 3fb60a89a3
commit b8552abcea
2 changed files with 16 additions and 11 deletions
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19
src/ripple/app/misc/impl/ValidatorSite.cpp
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@@ -167,9 +167,10 @@ ValidatorSite::load(
void
ValidatorSite::start()
{
std::lock_guard lock{state_mutex_};
std::lock_guard l0{sites_mutex_};
std::lock_guard l1{state_mutex_};
if (timer_.expires_at() == clock_type::time_point{})
setTimer(lock);
setTimer(l0, l1);
}
void
@@ -206,10 +207,10 @@ ValidatorSite::stop()
}
void
ValidatorSite::setTimer(std::lock_guard<std::mutex> const& state_lock)
ValidatorSite::setTimer(
std::lock_guard<std::mutex> const& site_lock,
std::lock_guard<std::mutex> const& state_lock)
{
std::lock_guard lock{sites_mutex_};
auto next = std::min_element(
sites_.begin(), sites_.end(), [](Site const& a, Site const& b) {
return a.nextRefresh < b.nextRefresh;
@@ -531,8 +532,8 @@ ValidatorSite::onSiteFetch(
detail::response_type&& res,
std::size_t siteIdx)
{
std::lock_guard lock_sites{sites_mutex_};
{
std::lock_guard lock_sites{sites_mutex_};
if (endpoint != endpoint_type{})
sites_[siteIdx].lastRequestEndpoint = endpoint;
JLOG(j_.debug()) << "Got completion for "
@@ -606,7 +607,7 @@ ValidatorSite::onSiteFetch(
std::lock_guard lock_state{state_mutex_};
fetching_ = false;
if (!stopping_)
setTimer(lock_state);
setTimer(lock_sites, lock_state);
cv_.notify_all();
}
@@ -616,8 +617,8 @@ ValidatorSite::onTextFetch(
std::string const& res,
std::size_t siteIdx)
{
std::lock_guard lock_sites{sites_mutex_};
{
std::lock_guard lock_sites{sites_mutex_};
try
{
if (ec)
@@ -643,7 +644,7 @@ ValidatorSite::onTextFetch(
std::lock_guard lock_state{state_mutex_};
fetching_ = false;
if (!stopping_)
setTimer(lock_state);
setTimer(lock_sites, lock_state);
cv_.notify_all();
}