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Add a default local latch for use in signal handlers.

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To do so, move InitializeLatchSupport() into the new common process
initialization functions, and add a new global variable MyLatch.

MyLatch is usable as soon InitPostmasterChild() has been called
(i.e. very early during startup). Initially it points to a process
local latch that exists in all processes. InitProcess/InitAuxiliaryProcess
then replaces that local latch with PGPROC->procLatch. During shutdown
the reverse happens.

This is primarily advantageous for two reasons: For one it simplifies
dealing with the shared process latch, especially in signal handlers,
because instead of having to check for MyProc, MyLatch can be used
unconditionally. For another, a later patch that makes FEs/BE
communication use latches, now can rely on the existence of a latch,
even before having gone through InitProcess.

Discussion: 20140927191243.GD5423@alap3.anarazel.de
This commit is contained in:
Andres Freund
2015-01-14 18:45:22 +01:00
parent 85a2a8903f
commit 59f71a0d0b
23 changed files with 136 additions and 134 deletions
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4
src/include/miscadmin.h
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@@ -148,6 +148,7 @@ extern int max_worker_processes;
extern PGDLLIMPORT int MyProcPid;
extern PGDLLIMPORT pg_time_t MyStartTime;
extern PGDLLIMPORT struct Port *MyProcPort;
extern PGDLLIMPORT struct Latch *MyLatch;
extern long MyCancelKey;
extern int MyPMChildSlot;
@@ -302,6 +303,9 @@ extern void SetCurrentRoleId(Oid roleid, bool is_superuser);
extern void SetDataDir(const char *dir);
extern void ChangeToDataDir(void);
extern void SwitchToSharedLatch(void);
extern void SwitchBackToLocalLatch(void);
/* in utils/misc/superuser.c */
extern bool superuser(void); /* current user is superuser */
extern bool superuser_arg(Oid roleid); /* given user is superuser */