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forkfd: dynamically detect whether the Darwin waitid is broken

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The Darwin kernel that came with Mac OS X 10.7 has a broken
implementation of waitid when passed a P_ALL first argument. It does
tell us that there is a process that can be wait()ed, but does not fill
in the siginfo_t structure.

See commit 9931fa9df4cb96a4006a3390db64f87e3b5bc1a0 for more
information.

Change-Id: Iee8cbc07c4434ce9b560ffff13cafa4c88cdabd6
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
This commit is contained in:
Thiago Macieira 2015-03-12 23:17:18 -07:00
parent bb5d287cc3
commit 4da46bbb9a
1 changed files with 31 additions and 4 deletions
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35
src/3rdparty/forkfd/forkfd.c vendored
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@ -58,6 +58,10 @@
# include <sys/eventfd.h>
#endif
#if _POSIX_VERSION-0 >= 200809L || _XOPEN_VERSION-0 >= 500
# define HAVE_WAITID 1
#endif
#if defined(__APPLE__)
/* Up until OS X 10.7, waitid(P_ALL, ...) will return success, but will not
* fill in the details of the dead child. That means waitid is not useful to us.
@ -66,11 +70,9 @@
*/
# include <Availability.h>
# include <AvailabilityMacros.h>
# if MAC_OS_X_VERSION_MIN_REQUIRED >= 1080
# define HAVE_WAITID 1
# if MAC_OS_X_VERSION_MIN_REQUIRED <= 1070
# define HAVE_BROKEN_WAITID_ALL 1
# endif
#elif _POSIX_VERSION-0 >= 200809L || _XOPEN_VERSION-0 >= 500
# define HAVE_WAITID 1
#endif
#ifndef FFD_ATOMIC_RELAXED
@ -115,6 +117,12 @@ static struct sigaction old_sigaction;
static pthread_once_t forkfd_initialization = PTHREAD_ONCE_INIT;
static ffd_atomic_int forkfd_status = FFD_ATOMIC_INIT(0);
#ifdef HAVE_BROKEN_WAITID_ALL
static int waitid_p_all_works = 0;
#else
static const int waitid_p_all_works = 1;
#endif
static ProcessInfo *tryAllocateInSection(Header *header, ProcessInfo entries[], int maxCount)
{
/* we use ACQUIRE here because the signal handler might have released the PID */
@ -246,6 +254,9 @@ static void sigchld_handler(int signum)
memset(&info, 0, sizeof info);
#ifdef HAVE_WAITID
if (!waitid_p_all_works)
goto search_arrays;
/* be optimistic: try to see if we can get the child that exited */
search_next_child:
/* waitid returns -1 ECHILD if there are no further children at all;
@ -298,6 +309,8 @@ search_next_child:
* belongs to one of the chained SIGCHLD handlers. However, there might be another
* child that exited and does belong to us, so we need to check each one individually.
*/
search_arrays:
#endif
for (i = 0; i < (int)sizeofarray(children.entries); ++i) {
@ -352,6 +365,20 @@ chain_handler:
static void forkfd_initialize()
{
#if defined(HAVE_BROKEN_WAITID_ALL)
pid_t pid = fork();
if (pid == 0) {
_exit(0);
} else if (pid > 0) {
siginfo_t info;
waitid(P_ALL, 0, &info, WNOWAIT | WEXITED);
waitid_p_all_works = (info.si_pid != 0);
// now really reap the child
waitid(P_PID, pid, &info, WEXITED);
}
#endif
/* install our signal handler */
struct sigaction action;
memset(&action, 0, sizeof action);