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c357be2cd9
Prevent handle_sig_alarm from losing control partway through due to a query cancel (either an asynchronous SIGINT, or a cancel triggered by one of the timeout handler functions). That would at least result in failure to schedule any required future interrupt, and might result in actual corruption of timeout.c's data structures, if the interrupt happened while we were updating those. We could still lose control if an asynchronous SIGINT arrives just as the function is entered. This wouldn't break any data structures, but it would have the same effect as if the SIGALRM interrupt had been silently lost: we'd not fire any currently-due handlers, nor schedule any new interrupt. To forestall that scenario, forcibly reschedule any pending timer interrupt during AbortTransaction and AbortSubTransaction. We can avoid any extra kernel call in most cases by not doing that until we've allowed LockErrorCleanup to kill the DEADLOCK_TIMEOUT and LOCK_TIMEOUT events. Another hazard is that some platforms (at least Linux and *BSD) block a signal before calling its handler and then unblock it on return. When we longjmp out of the handler, the unblock doesn't happen, and the signal is left blocked indefinitely. Again, we can fix that by forcibly unblocking signals during AbortTransaction and AbortSubTransaction. These latter two problems do not manifest when the longjmp reaches postgres.c, because the error recovery code there kills all pending timeout events anyway, and it uses sigsetjmp(..., 1) so that the appropriate signal mask is restored. So errors thrown outside any transaction should be OK already, and cleaning up in AbortTransaction and AbortSubTransaction should be enough to fix these issues. (We're assuming that any code that catches a query cancel error and doesn't re-throw it will do at least a subtransaction abort to clean up; but that was pretty much required already by other subsystems.) Lastly, ProcSleep should not clear the LOCK_TIMEOUT indicator flag when disabling that event: if a lock timeout interrupt happened after the lock was granted, the ensuing query cancel is still going to happen at the next CHECK_FOR_INTERRUPTS, and we want to report it as a lock timeout not a user cancel. Per reports from Dan Wood. Back-patch to 9.3 where the new timeout handling infrastructure was introduced. We may at some point decide to back-patch the signal unblocking changes further, but I'll desist from that until we hear actual field complaints about it.
84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* timeout.h
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* Routines to multiplex SIGALRM interrupts for multiple timeout reasons.
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*
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*
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* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/timeout.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef TIMEOUT_H
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#define TIMEOUT_H
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#include "datatype/timestamp.h"
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/*
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* Identifiers for timeout reasons. Note that in case multiple timeouts
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* trigger at the same time, they are serviced in the order of this enum.
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*/
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typedef enum TimeoutId
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{
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/* Predefined timeout reasons */
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STARTUP_PACKET_TIMEOUT,
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DEADLOCK_TIMEOUT,
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LOCK_TIMEOUT,
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STATEMENT_TIMEOUT,
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STANDBY_DEADLOCK_TIMEOUT,
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STANDBY_TIMEOUT,
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/* First user-definable timeout reason */
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USER_TIMEOUT,
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/* Maximum number of timeout reasons */
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MAX_TIMEOUTS = 16
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} TimeoutId;
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/* callback function signature */
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typedef void (*timeout_handler_proc) (void);
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/*
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* Parameter structure for setting multiple timeouts at once
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*/
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typedef enum TimeoutType
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{
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TMPARAM_AFTER,
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TMPARAM_AT
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} TimeoutType;
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typedef struct
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{
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TimeoutId id; /* timeout to set */
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TimeoutType type; /* TMPARAM_AFTER or TMPARAM_AT */
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int delay_ms; /* only used for TMPARAM_AFTER */
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TimestampTz fin_time; /* only used for TMPARAM_AT */
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} EnableTimeoutParams;
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/*
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* Parameter structure for clearing multiple timeouts at once
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*/
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typedef struct
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{
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TimeoutId id; /* timeout to clear */
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bool keep_indicator; /* keep the indicator flag? */
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} DisableTimeoutParams;
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/* timeout setup */
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extern void InitializeTimeouts(void);
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extern TimeoutId RegisterTimeout(TimeoutId id, timeout_handler_proc handler);
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extern void reschedule_timeouts(void);
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/* timeout operation */
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extern void enable_timeout_after(TimeoutId id, int delay_ms);
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extern void enable_timeout_at(TimeoutId id, TimestampTz fin_time);
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extern void enable_timeouts(const EnableTimeoutParams *timeouts, int count);
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extern void disable_timeout(TimeoutId id, bool keep_indicator);
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extern void disable_timeouts(const DisableTimeoutParams *timeouts, int count);
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extern void disable_all_timeouts(bool keep_indicators);
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/* accessors */
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extern bool get_timeout_indicator(TimeoutId id, bool reset_indicator);
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extern TimestampTz get_timeout_start_time(TimeoutId id);
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#endif /* TIMEOUT_H */
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