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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build unix
package syscall
import (
"sync/atomic"
)
// origRlimitNofile, if not {0, 0}, is the original soft RLIMIT_NOFILE.
// When we can assume that we are bootstrapping with Go 1.19,
// this can be atomic.Pointer[Rlimit].
var origRlimitNofile atomic.Value // of Rlimit
// Some systems set an artificially low soft limit on open file count, for compatibility
// with code that uses select and its hard-coded maximum file descriptor
// (limited by the size of fd_set).
//
// Go does not use select, so it should not be subject to these limits.
// On some systems the limit is 256, which is very easy to run into,
// even in simple programs like gofmt when they parallelize walking
// a file tree.
//
// After a long discussion on go.dev/issue/46279, we decided the
// best approach was for Go to raise the limit unconditionally for itself,
// and then leave old software to set the limit back as needed.
// Code that really wants Go to leave the limit alone can set the hard limit,
// which Go of course has no choice but to respect.
func init() {
var lim Rlimit
if err := Getrlimit(RLIMIT_NOFILE, &lim); err == nil && lim.Cur != lim.Max {
origRlimitNofile.Store(lim)
lim.Cur = lim.Max
adjustFileLimit(&lim)
setrlimit(RLIMIT_NOFILE, &lim)
}
}
func Setrlimit(resource int, rlim *Rlimit) error {
err := setrlimit(resource, rlim)
if err == nil && resource == RLIMIT_NOFILE {
// Store zeroes in origRlimitNofile to tell StartProcess
// to not adjust the rlimit in the child process.
origRlimitNofile.Store(Rlimit{0, 0})
}
return err
}
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