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Commit24ecde7

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Work around unfortunate getppid() behavior on BSD-ish systems.
On MacOS X, and apparently also on other BSD-derived systems, attachinga debugger causes getppid() to return the pid of the debugging processrather than the actual parent PID. As a result, debugging theautovacuum launcher, startup process, or WAL sender on such systemscauses 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-reliablekill() test.Review by Tom Lane.
1 parentf6a0863 commit24ecde7

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‎src/backend/storage/ipc/pmsignal.c

Lines changed: 21 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -260,22 +260,30 @@ PostmasterIsAlive(bool amDirectChild)
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#ifndefWIN32
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if (amDirectChild)
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{
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pid_tppid=getppid();
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/* If the postmaster is still our parent, it must be alive. */
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if (ppid==PostmasterPid)
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return true;
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/* If the init process is our parent, postmaster must be dead. */
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if (ppid==1)
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return false;
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/*
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* If the postmaster is alive, we'll still be its child. If it's
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* died, we'll be reassigned as a child of the init process.
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*/
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return (getppid()==PostmasterPid);
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}
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else
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{
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/*
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* Use kill() to see if the postmaster is still alive.This can
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* sometimes give a false positive result, since the postmaster's PID
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* may get recycled, but it is good enough for existing uses by
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* indirect children.
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* If we get here, our parent process is neither the postmaster nor
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* init. This can occur on BSD and MacOS systems if a debugger has
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* been attached. We fall through to the less-reliable kill() method.
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*/
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return (kill(PostmasterPid,0)==0);
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}
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/*
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* Use kill() to see if the postmaster is still alive.This can
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* sometimes give a false positive result, since the postmaster's PID
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* may get recycled, but it is good enough for existing uses by
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* indirect children and in debugging environments.
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*/
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return (kill(PostmasterPid,0)==0);
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#else/* WIN32 */
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return (WaitForSingleObject(PostmasterHandle,0)==WAIT_TIMEOUT);
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#endif/* WIN32 */

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