| title | C26138 | |
|---|---|---|
| ms.date | 01/14/2019 | |
| ms.topic | reference | |
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| author | sunnychatterjee | |
| ms.author | sunnych |
warning C26138: Suspending a coroutine while holding lock <lock>.
Warning C26138 warns when a coroutine is suspended while holding a lock. In general, we can't know how long will a coroutine remain in the suspended state so this pattern may result in longer critical sections than expected.
The following code will generate C26138.
#include <experimental/generator>
#include <future>
#include <mutex>
using namespace std::experimental;
std::mutex global_m;
_Guarded_by_(global_m) int var = 0;
generator<int> mutex_acquiring_generator() {
global_m.lock();
++var;
co_yield 1; // @expected(26138), global_m is hold while yielding.
global_m.unlock();
}
generator<int> mutex_acquiring_generator_report_once() {
global_m.lock();
++var;
co_yield 1; // @expected(26138), global_m is hold while yielding.
co_yield 1; // @expected(26138), global_m is hold while yielding.
global_m.unlock();
}The following code will correct these warnings.
#include <experimental/generator>
#include <future>
#include <mutex>
using namespace std::experimental;
std::mutex global_m;
_Guarded_by_(global_m) int var = 0;
generator<int> mutex_acquiring_generator2() {
{
global_m.lock();
++var;
global_m.unlock();
}
co_yield 1; // no 26138, global_m is already released above.
}