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pqsignal.c
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1 /*-------------------------------------------------------------------------
2  *
3  * pqsignal.c
4  * Backend signal(2) support (see also src/port/pqsignal.c)
5  *
6  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  *
10  * IDENTIFICATION
11  * src/backend/libpq/pqsignal.c
12  *
13  * ------------------------------------------------------------------------
14  */
15 
16 #include "postgres.h"
17 
18 #include "libpq/pqsignal.h"
19 
20 
21 /* Global variables */
22 sigset_t UnBlockSig,
23  BlockSig,
25 
26 
27 /*
28  * Initialize BlockSig, UnBlockSig, and StartupBlockSig.
29  *
30  * BlockSig is the set of signals to block when we are trying to block
31  * signals. This includes all signals we normally expect to get, but NOT
32  * signals that should never be turned off.
33  *
34  * StartupBlockSig is the set of signals to block during startup packet
35  * collection; it's essentially BlockSig minus SIGTERM, SIGQUIT, SIGALRM.
36  *
37  * UnBlockSig is the set of signals to block when we don't want to block
38  * signals (is this ever nonzero??)
39  */
40 void
42 {
43  sigemptyset(&UnBlockSig);
44 
45  /* First set all signals, then clear some. */
46  sigfillset(&BlockSig);
47  sigfillset(&StartupBlockSig);
48 
49  /*
50  * Unmark those signals that should never be blocked. Some of these signal
51  * names don't exist on all platforms. Most do, but might as well ifdef
52  * them all for consistency...
53  */
54 #ifdef SIGTRAP
55  sigdelset(&BlockSig, SIGTRAP);
56  sigdelset(&StartupBlockSig, SIGTRAP);
57 #endif
58 #ifdef SIGABRT
59  sigdelset(&BlockSig, SIGABRT);
60  sigdelset(&StartupBlockSig, SIGABRT);
61 #endif
62 #ifdef SIGILL
63  sigdelset(&BlockSig, SIGILL);
64  sigdelset(&StartupBlockSig, SIGILL);
65 #endif
66 #ifdef SIGFPE
67  sigdelset(&BlockSig, SIGFPE);
68  sigdelset(&StartupBlockSig, SIGFPE);
69 #endif
70 #ifdef SIGSEGV
71  sigdelset(&BlockSig, SIGSEGV);
72  sigdelset(&StartupBlockSig, SIGSEGV);
73 #endif
74 #ifdef SIGBUS
75  sigdelset(&BlockSig, SIGBUS);
76  sigdelset(&StartupBlockSig, SIGBUS);
77 #endif
78 #ifdef SIGSYS
79  sigdelset(&BlockSig, SIGSYS);
80  sigdelset(&StartupBlockSig, SIGSYS);
81 #endif
82 #ifdef SIGCONT
83  sigdelset(&BlockSig, SIGCONT);
84  sigdelset(&StartupBlockSig, SIGCONT);
85 #endif
86 
87 /* Signals unique to startup */
88 #ifdef SIGQUIT
89  sigdelset(&StartupBlockSig, SIGQUIT);
90 #endif
91 #ifdef SIGTERM
92  sigdelset(&StartupBlockSig, SIGTERM);
93 #endif
94 #ifdef SIGALRM
95  sigdelset(&StartupBlockSig, SIGALRM);
96 #endif
97 }
98 
99 /*
100  * Set up a postmaster signal handler for signal "signo"
101  *
102  * Returns the previous handler.
103  *
104  * This is used only in the postmaster, which has its own odd approach to
105  * signal handling. For signals with handlers, we block all signals for the
106  * duration of signal handler execution. We also do not set the SA_RESTART
107  * flag; this should be safe given the tiny range of code in which the
108  * postmaster ever unblocks signals.
109  *
110  * pqinitmask() must have been invoked previously.
111  *
112  * On Windows, this function is just an alias for pqsignal()
113  * (and note that it's calling the code in src/backend/port/win32/signal.c,
114  * not src/port/pqsignal.c). On that platform, the postmaster's signal
115  * handlers still have to block signals for themselves.
116  */
117 pqsigfunc
118 pqsignal_pm(int signo, pqsigfunc func)
119 {
120 #ifndef WIN32
121  struct sigaction act,
122  oact;
123 
124  act.sa_handler = func;
125  if (func == SIG_IGN || func == SIG_DFL)
126  {
127  /* in these cases, act the same as pqsignal() */
128  sigemptyset(&act.sa_mask);
129  act.sa_flags = SA_RESTART;
130  }
131  else
132  {
133  act.sa_mask = BlockSig;
134  act.sa_flags = 0;
135  }
136 #ifdef SA_NOCLDSTOP
137  if (signo == SIGCHLD)
138  act.sa_flags |= SA_NOCLDSTOP;
139 #endif
140  if (sigaction(signo, &act, &oact) < 0)
141  return SIG_ERR;
142  return oact.sa_handler;
143 #else /* WIN32 */
144  return pqsignal(signo, func);
145 #endif
146 }
pqsigfunc pqsignal(int signo, pqsigfunc func)
Definition: pqsignal.c:40
#define SIGQUIT
Definition: win32_port.h:155
#define SIGCHLD
Definition: win32_port.h:164
void(* pqsigfunc)(int signo)
Definition: port.h:526
#define SIGCONT
Definition: win32_port.h:163
#define SIGTRAP
Definition: win32_port.h:156
#define SIG_ERR
Definition: win32_port.h:150
#define SIGABRT
Definition: win32_port.h:157
void pqinitmask(void)
Definition: pqsignal.c:41
sigset_t UnBlockSig
Definition: pqsignal.c:22
#define SIG_IGN
Definition: win32_port.h:151
pqsigfunc pqsignal_pm(int signo, pqsigfunc func)
Definition: pqsignal.c:118
sigset_t BlockSig
Definition: pqsignal.c:22
#define SIG_DFL
Definition: win32_port.h:149
#define SIGALRM
Definition: win32_port.h:160
sigset_t StartupBlockSig
Definition: pqsignal.c:22