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authorKeith Owens <k10@ocs.com.au>2011-09-16 17:55:28 +0200
committerStef Walter <stefw@collabora.co.uk>2011-09-16 17:55:28 +0200
commit52747cc1752b8a8e35aee47db2f55d3a3c365ce3 (patch)
treeb5085f6338d3bbb57c7f2f58388765b2dc28ccde /src/proxsmtpd.c
parent1994fa733c1c09202d85db952a28da26a19f0669 (diff)
workaround for race between waitpid(-1) and waitpid(pid)
Sometimes waitpid(-1) in cb_check_data reaps a child that has just terminated, before waitpid(pid) in wait_process can reap it. Linux waitpid(pid,,WNOHANG) may not return an error if the child has already terminated, which results in wait_process looping waiting for the child which has already terminated. The symptom is a spurious "timeout waiting for filter command to exit".
Diffstat (limited to 'src/proxsmtpd.c')
-rw-r--r--src/proxsmtpd.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/src/proxsmtpd.c b/src/proxsmtpd.c
index 278ecee..8f50d96 100644
--- a/src/proxsmtpd.c
+++ b/src/proxsmtpd.c
@@ -925,6 +925,11 @@ static int wait_process(spctx_t* sp, pid_t pid, int* status)
switch(waitpid(pid, status, WNOHANG))
{
case 0:
+ /* Linux may return 0 if the task has already terminated and was
+ * caught by waitpid(-1) above, double check it still exists.
+ */
+ if (kill(pid, 0) < 0 && errno == ESRCH)
+ return 0;
break;
case -1:
if(errno != ECHILD && errno != ESRCH)