path: root/src/include
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authorRich Felker <>2019-02-16 09:13:45 -0500
committerRich Felker <>2019-02-16 10:11:22 -0500
commite4235d70672d9751d7718ddc2b52d0b426430768 (patch)
treecf4d965f2a440b641adca6fd3ddf5f17278e3210 /src/include
parent8f11e6127fe93093f81a52b15bb1537edc3fc8af (diff)
rewrite __synccall in terms of global thread list
the __synccall mechanism provides stop-the-world synchronous execution of a callback in all threads of the process. it is used to implement multi-threaded setuid/setgid operations, since Linux lacks them at the kernel level, and for some other less-critical purposes. this change eliminates dependency on /proc/self/task to determine the set of live threads, which in addition to being an unwanted dependency and a potential point of resource-exhaustion failure, turned out to be inaccurate. test cases provided by Alexey Izbyshev showed that it could fail to reflect newly created threads. due to how the presignaling phase worked, this usually yielded a deadlock if hit, but in the worst case it could also result in threads being silently missed (allowed to continue running without executing the callback).
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