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Work around unfortunate getppid() behavior on BSD-ish systems.

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On MacOS X, and apparently also on other BSD-derived systems, attaching
a debugger causes getppid() to return the pid of the debugging process
rather than the actual parent PID.  As a result, debugging the
autovacuum launcher, startup process, or WAL sender on such systems
causes it to exit, because the previous coding of PostmasterIsAlive()
detects postmaster death by testing whether getppid() == PostmasterPid.

Work around that behavior by checking the return value of getppid()
more carefully.  If it's PostmasterPid, the postmaster must be alive;
if it's 1, assume the postmaster is dead.  If it's any other value,
assume we've been debugged and fall through to the less-reliable
kill() test.

Review by Tom Lane.
This commit is contained in:
Robert Haas
2010-12-21 06:30:32 -05:00
parent f6a0863e3c
commit 24ecde7742
1 changed files with 21 additions and 13 deletions
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34
src/backend/storage/ipc/pmsignal.c
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@ -260,22 +260,30 @@ PostmasterIsAlive(bool amDirectChild)
#ifndef WIN32
if (amDirectChild)
{
pid_t ppid = getppid();
/* If the postmaster is still our parent, it must be alive. */
if (ppid == PostmasterPid)
return true;
/* If the init process is our parent, postmaster must be dead. */
if (ppid == 1)
return false;
/*
* If the postmaster is alive, we'll still be its child. If it's
* died, we'll be reassigned as a child of the init process.
* If we get here, our parent process is neither the postmaster nor
* init. This can occur on BSD and MacOS systems if a debugger has
* been attached. We fall through to the less-reliable kill() method.
*/
return (getppid() == PostmasterPid);
}
else
{
/*
* Use kill() to see if the postmaster is still alive. This can
* sometimes give a false positive result, since the postmaster's PID
* may get recycled, but it is good enough for existing uses by
* indirect children.
*/
return (kill(PostmasterPid, 0) == 0);
}
/*
* Use kill() to see if the postmaster is still alive. This can
* sometimes give a false positive result, since the postmaster's PID
* may get recycled, but it is good enough for existing uses by
* indirect children and in debugging environments.
*/
return (kill(PostmasterPid, 0) == 0);
#else /* WIN32 */
return (WaitForSingleObject(PostmasterHandle, 0) == WAIT_TIMEOUT);
#endif /* WIN32 */