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Remove set_latch_on_sigusr1 flag.

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This flag has proven to be a recipe for bugs, and it doesn't seem like
it can really buy anything in terms of performance.  So let's just
*always* set the process latch when we receive SIGUSR1 instead of
trying to do it only when needed.

Per my recent proposal on pgsql-hackers.
This commit is contained in:
Robert Haas 2015-10-09 14:31:04 -04:00
parent b7aac36245
commit db0f6cad48
6 changed files with 91 additions and 158 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
src/backend/postmaster/bgworker.c
View File

@ -954,13 +954,7 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
{
BgwHandleStatus status;
int rc;
bool save_set_latch_on_sigusr1;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
set_latch_on_sigusr1 = true;
PG_TRY();
{
for (;;)
{
pid_t pid;
@ -984,15 +978,7 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
ResetLatch(MyLatch);
}
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
return status;
}
@ -1009,13 +995,7 @@ WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *handle)
{
BgwHandleStatus status;
int rc;
bool save_set_latch_on_sigusr1;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
set_latch_on_sigusr1 = true;
PG_TRY();
{
for (;;)
{
pid_t pid;
@ -1034,15 +1014,7 @@ WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *handle)
ResetLatch(&MyProc->procLatch);
}
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
return status;
}

9
src/backend/storage/ipc/procsignal.c
View File

@ -59,14 +59,6 @@ typedef struct
*/
#define NumProcSignalSlots (MaxBackends + NUM_AUXPROCTYPES)
/*
* If this flag is set, the process latch will be set whenever SIGUSR1
* is received. This is useful when waiting for a signal from the postmaster.
* Spurious wakeups must be expected. Make sure that the flag is cleared
* in the error path.
*/
bool set_latch_on_sigusr1;
static ProcSignalSlot *ProcSignalSlots = NULL;
static volatile ProcSignalSlot *MyProcSignalSlot = NULL;
@ -296,7 +288,6 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
if (set_latch_on_sigusr1)
SetLatch(MyLatch);
latch_sigusr1_handler();

14
src/backend/storage/ipc/shm_mq.c
View File

@ -962,15 +962,8 @@ static bool
shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile * ptr,
BackgroundWorkerHandle *handle)
{
bool save_set_latch_on_sigusr1;
bool result = false;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
if (handle != NULL)
set_latch_on_sigusr1 = true;
PG_TRY();
{
for (;;)
{
BgwHandleStatus status;
@ -1012,13 +1005,6 @@ shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile * ptr,
/* Reset the latch so we don't spin. */
ResetLatch(MyLatch);
}
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
return result;
}

4
src/backend/tcop/postgres.c
View File

@ -2825,9 +2825,7 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
/*
* Set the process latch. This function essentially emulates signal
* handlers like die() and StatementCancelHandler() and it seems prudent
* to behave similarly as they do. Alternatively all plain backend code
* waiting on that latch, expecting to get interrupted by query cancels et
* al., would also need to set set_latch_on_sigusr1.
* to behave similarly as they do.
*/
SetLatch(MyLatch);

1
src/include/storage/procsignal.h
View File

@ -55,6 +55,5 @@ extern int SendProcSignal(pid_t pid, ProcSignalReason reason,
BackendId backendId);
extern void procsignal_sigusr1_handler(SIGNAL_ARGS);
extern PGDLLIMPORT bool set_latch_on_sigusr1;
#endif /* PROCSIGNAL_H */

13
src/test/modules/test_shm_mq/setup.c
View File

@ -255,14 +255,8 @@ static void
wait_for_workers_to_become_ready(worker_state *wstate,
volatile test_shm_mq_header *hdr)
{
bool save_set_latch_on_sigusr1;
bool result = false;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
set_latch_on_sigusr1 = true;
PG_TRY();
{
for (;;)
{
int workers_ready;
@ -293,13 +287,6 @@ wait_for_workers_to_become_ready(worker_state *wstate,
/* Reset the latch so we don't spin. */
ResetLatch(MyLatch);
}
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
if (!result)
ereport(ERROR,