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Fix a race in maintaining the journald reader list

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The journald log reader keeps a map of following readers so that it can
close them properly when the journald reader object itself is closed,
but it was possible for its worker goroutine to be scheduled so that the
worker attempted to remove a reader from the map before the reader had
been added to the map.  This patch adds the item to the map before
starting the goroutine which is expected to eventually remove it.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com> (github: nalind)
This commit is contained in:
Nalin Dahyabhai 2016-03-17 16:17:11 -04:00
parent 41c1c6501e
commit 4d200cd693
1 changed files with 3 additions and 3 deletions
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6
daemon/logger/journald/read.go
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@ -173,6 +173,9 @@ drain:
} }
func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.ReadConfig, j *C.sd_journal, pfd [2]C.int, cursor string) { func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.ReadConfig, j *C.sd_journal, pfd [2]C.int, cursor string) {
s.readers.mu.Lock()
s.readers.readers[logWatcher] = logWatcher
s.readers.mu.Unlock()
go func() { go func() {
// Keep copying journal data out until we're notified to stop. // Keep copying journal data out until we're notified to stop.
for C.wait_for_data_or_close(j, pfd[0]) == 1 { for C.wait_for_data_or_close(j, pfd[0]) == 1 {
@ -184,9 +187,6 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.Re
delete(s.readers.readers, logWatcher) delete(s.readers.readers, logWatcher)
s.readers.mu.Unlock() s.readers.mu.Unlock()
}() }()
s.readers.mu.Lock()
s.readers.readers[logWatcher] = logWatcher
s.readers.mu.Unlock()
// Wait until we're told to stop. // Wait until we're told to stop.
select { select {
case <-logWatcher.WatchClose(): case <-logWatcher.WatchClose():