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Eventloop: Fix deadlock in linux event loop implementation

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A simple empty main with evented-io would not quit, because some
threads were still waiting to be resumed (by the os). The os.write to
the eventfd only wakes up one thread and thus there are multiple writes
needed to wake up all the other threads.
This commit is contained in:
Timon Kruiper 2020-09-23 11:41:31 +02:00
parent 58ee5f4e61
commit 0eed7ec9d5
1 changed files with 8 additions and 3 deletions
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11
lib/std/event/loop.zig
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@ -687,9 +687,14 @@ pub const Loop = struct {
switch (builtin.os.tag) {
.linux => {
// writing 8 bytes to an eventfd cannot fail
const amt = os.write(self.os_data.final_eventfd, &wakeup_bytes) catch unreachable;
assert(amt == wakeup_bytes.len);
// writing to the eventfd will only wake up one thread, thus multiple writes
// are needed to wakeup all the threads
var i: usize = 0;
while (i < self.extra_threads.len + 1) : (i += 1) {
// writing 8 bytes to an eventfd cannot fail
const amt = os.write(self.os_data.final_eventfd, &wakeup_bytes) catch unreachable;
assert(amt == wakeup_bytes.len);
}
return;
},
.macosx, .freebsd, .netbsd, .dragonfly => {