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package main
import (
"fmt"
"path/filepath"
"syscall"
)
// flockBasic exercises the flock syscall end-to-end. It opens a temp file,
// acquires an exclusive advisory lock (LOCK_EX), releases it (LOCK_UN), then
// closes the file and removes the temp dir.
//
// flock is unprivileged (FamilyFS) and captured as KindFd at args[0]; ior
// resolves that fd to the underlying file path via the procfd cache, so the
// enter_flock record carries the temp filename. Its return value is
// UNCLASSIFIED (0 on success), so this scenario only locks in the enter path.
func flockBasic() error {
dir, cleanup, err := makeTempDir("flock-basic")
if err != nil {
return err
}
defer cleanup()
path := filepath.Join(dir, "flockfile.txt")
fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT, 0o644)
if err != nil {
return fmt.Errorf("open: %w", err)
}
defer syscall.Close(fd)
// Use raw syscall.Flock so the exact sys_enter_flock tracepoint fires.
if err := syscall.Flock(fd, syscall.LOCK_EX); err != nil {
return fmt.Errorf("flock LOCK_EX: %w", err)
}
if err := syscall.Flock(fd, syscall.LOCK_UN); err != nil {
return fmt.Errorf("flock LOCK_UN: %w", err)
}
return nil
}
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