.\" and Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
.\"
.\" Modified Sat Jul 24 17:34:08 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified Sun Jan 7 01:41:27 1996 by Andries Brouwer (aeb@cwi.nl)
.\" 2008-07-04, mtk:
.\" Added section on system call restarting (SA_RESTART)
.\" Added section on stop/cont signals interrupting syscalls.
+.\" 2008-10-05, mtk: various additions
.\"
-.TH SIGNAL 7 2008-07-07 "Linux" "Linux Programmer's Manual"
+.TH SIGNAL 7 2019-03-06 "Linux" "Linux Programmer's Manual"
.SH NAME
-signal \- list of available signals
+signal \- overview of signals
.SH DESCRIPTION
Linux supports both POSIX reliable signals (hereinafter
"standard signals") and POSIX real-time signals.
-.SS "Signal Dispositions"
+.SS Signal dispositions
Each signal has a current
.IR disposition ,
which determines how the process behaves when it is delivered
the signal.
-
-The entries in the "Action" column of the tables below specify
+.PP
+The entries in the "Action" column of the table below specify
the default disposition for each signal, as follows:
.IP Term
Default action is to terminate the process.
.PP
A process can change the disposition of a signal using
.BR sigaction (2)
-or (less portably)
+or
.BR signal (2).
+(The latter is less portable when establishing a signal handler;
+see
+.BR signal (2)
+for details.)
Using these system calls, a process can elect one of the
following behaviors to occur on delivery of the signal:
perform the default action; ignore the signal;
.IR "signal handler" ,
a programmer-defined function that is automatically invoked
when the signal is delivered.
-
+(By default, the signal handler is invoked on the
+normal process stack.
+It is possible to arrange that the signal handler
+uses an alternate stack; see
+.BR sigaltstack (2)
+for a discussion of how to do this and when it might be useful.)
+.PP
The signal disposition is a per-process attribute:
in a multithreaded application, the disposition of a
particular signal is the same for all threads.
-.SS "Signal Mask and Pending Signals"
+.PP
+A child created via
+.BR fork (2)
+inherits a copy of its parent's signal dispositions.
+During an
+.BR execve (2),
+the dispositions of handled signals are reset to the default;
+the dispositions of ignored signals are left unchanged.
+.SS Sending a signal
+The following system calls and library functions allow
+the caller to send a signal:
+.TP 16
+.BR raise (3)
+Sends a signal to the calling thread.
+.TP
+.BR kill (2)
+Sends a signal to a specified process,
+to all members of a specified process group,
+or to all processes on the system.
+.TP
+.BR killpg (3)
+Sends a signal to all of the members of a specified process group.
+.TP
+.BR pthread_kill (3)
+Sends a signal to a specified POSIX thread in the same process as
+the caller.
+.TP
+.BR tgkill (2)
+Sends a signal to a specified thread within a specific process.
+(This is the system call used to implement
+.BR pthread_kill (3).)
+.TP
+.BR sigqueue (3)
+Sends a real-time signal with accompanying data to a specified process.
+.SS Waiting for a signal to be caught
+The following system calls suspend execution of the calling
+thread until a signal is caught
+(or an unhandled signal terminates the process):
+.TP 16
+.BR pause (2)
+Suspends execution until any signal is caught.
+.TP
+.BR sigsuspend (2)
+Temporarily changes the signal mask (see below) and suspends
+execution until one of the unmasked signals is caught.
+.SS Synchronously accepting a signal
+Rather than asynchronously catching a signal via a signal handler,
+it is possible to synchronously accept the signal, that is,
+to block execution until the signal is delivered,
+at which point the kernel returns information about the
+signal to the caller.
+There are two general ways to do this:
+.IP * 2
+.BR sigwaitinfo (2),
+.BR sigtimedwait (2),
+and
+.BR sigwait (3)
+suspend execution until one of the signals in a specified
+set is delivered.
+Each of these calls returns information about the delivered signal.
+.IP *
+.BR signalfd (2)
+returns a file descriptor that can be used to read information
+about signals that are delivered to the caller.
+Each
+.BR read (2)
+from this file descriptor blocks until one of the signals
+in the set specified in the
+.BR signalfd (2)
+call is delivered to the caller.
+The buffer returned by
+.BR read (2)
+contains a structure describing the signal.
+.SS Signal mask and pending signals
A signal may be
.IR blocked ,
which means that it will not be delivered until it is later unblocked.
Between the time when it is generated and when it is delivered
a signal is said to be
.IR pending .
-
+.PP
Each thread in a process has an independent
.IR "signal mask" ,
which indicates the set of signals that the thread is currently blocking.
In a traditional single-threaded application,
.BR sigprocmask (2)
can be used to manipulate the signal mask.
-
+.PP
+A child created via
+.BR fork (2)
+inherits a copy of its parent's signal mask;
+the signal mask is preserved across
+.BR execve (2).
+.PP
A signal may be generated (and thus pending)
for a process as a whole (e.g., when sent using
.BR kill (2))
threads that does not currently have the signal blocked.
If more than one of the threads has the signal unblocked, then the
kernel chooses an arbitrary thread to which to deliver the signal.
-
+.PP
A thread can obtain the set of signals that it currently has pending
using
.BR sigpending (2).
This set will consist of the union of the set of pending
process-directed signals and the set of signals pending for
the calling thread.
-.SS "Standard Signals"
+.PP
+A child created via
+.BR fork (2)
+initially has an empty pending signal set;
+the pending signal set is preserved across an
+.BR execve (2).
+.SS Standard signals
Linux supports the standard signals listed below.
-Several signal numbers
-are architecture-dependent, as indicated in the "Value" column.
-(Where three values are given, the first one is usually valid for
-alpha and sparc,
-the middle one for ix86, ia64, ppc, s390, arm and sh,
-and the last one for mips.
-.\" parisc is a law unto itself
-A \- denotes that a signal is absent on the corresponding architecture.)
-
-First the signals described in the original POSIX.1-1990 standard.
+The second column of the table indicates which standard (if any)
+specified the signal: "P1990" indicates that the signal is described
+in the original POSIX.1-1990 standard;
+"P2001" indicates that the signal was added in SUSv2 and POSIX.1-2001.
.TS
l c c l
____
lB c c l.
-Signal Value Action Comment
-SIGHUP \01 Term Hangup detected on controlling terminal
+Signal Standard Action Comment
+SIGABRT P1990 Core Abort signal from \fBabort\fP(3)
+SIGALRM P1990 Term Timer signal from \fBalarm\fP(2)
+SIGBUS P2001 Core Bus error (bad memory access)
+SIGCHLD P1990 Ign Child stopped or terminated
+SIGCLD \- Ign A synonym for \fBSIGCHLD\fP
+SIGCONT P1990 Cont Continue if stopped
+SIGEMT \- Term Emulator trap
+SIGFPE P1990 Core Floating-point exception
+SIGHUP P1990 Term Hangup detected on controlling terminal
or death of controlling process
-SIGINT \02 Term Interrupt from keyboard
-SIGQUIT \03 Core Quit from keyboard
-SIGILL \04 Core Illegal Instruction
-SIGABRT \06 Core Abort signal from \fBabort\fP(3)
-SIGFPE \08 Core Floating point exception
-SIGKILL \09 Term Kill signal
-SIGSEGV 11 Core Invalid memory reference
-SIGPIPE 13 Term Broken pipe: write to pipe with no
- readers
-SIGALRM 14 Term Timer signal from \fBalarm\fP(2)
-SIGTERM 15 Term Termination signal
-SIGUSR1 30,10,16 Term User-defined signal 1
-SIGUSR2 31,12,17 Term User-defined signal 2
-SIGCHLD 20,17,18 Ign Child stopped or terminated
-SIGCONT 19,18,25 Cont Continue if stopped
-SIGSTOP 17,19,23 Stop Stop process
-SIGTSTP 18,20,24 Stop Stop typed at tty
-SIGTTIN 21,21,26 Stop tty input for background process
-SIGTTOU 22,22,27 Stop tty output for background process
+SIGILL P1990 Core Illegal Instruction
+SIGINFO \- A synonym for \fBSIGPWR\fP
+SIGINT P1990 Term Interrupt from keyboard
+SIGIO \- Term I/O now possible (4.2BSD)
+SIGIOT \- Core IOT trap. A synonym for \fBSIGABRT\fP
+SIGKILL P1990 Term Kill signal
+SIGLOST \- Term File lock lost (unused)
+SIGPIPE P1990 Term Broken pipe: write to pipe with no
+ readers; see \fBpipe\fP(7)
+SIGPOLL P2001 Term Pollable event (Sys V).
+ Synonym for \fBSIGIO\fP
+SIGPROF P2001 Term Profiling timer expired
+SIGPWR \- Term Power failure (System V)
+SIGQUIT P1990 Core Quit from keyboard
+SIGSEGV P1990 Core Invalid memory reference
+SIGSTKFLT \- Term Stack fault on coprocessor (unused)
+SIGSTOP P1990 Stop Stop process
+SIGTSTP P1990 Stop Stop typed at terminal
+SIGSYS P2001 Core Bad system call (SVr4);
+ see also \fBseccomp\fP(2)
+SIGTERM P1990 Term Termination signal
+SIGTRAP P2001 Core Trace/breakpoint trap
+SIGTTIN P1990 Stop Terminal input for background process
+SIGTTOU P1990 Stop Terminal output for background process
+SIGUNUSED \- Core Synonymous with \fBSIGSYS\fP
+SIGURG P2001 Ign Urgent condition on socket (4.2BSD)
+SIGUSR1 P1990 Term User-defined signal 1
+SIGUSR2 P1990 Term User-defined signal 2
+SIGVTALRM P2001 Term Virtual alarm clock (4.2BSD)
+SIGXCPU P2001 Core CPU time limit exceeded (4.2BSD);
+ see \fBsetrlimit\fP(2)
+SIGXFSZ P2001 Core File size limit exceeded (4.2BSD);
+ see \fBsetrlimit\fP(2)
+SIGWINCH \- Ign Window resize signal (4.3BSD, Sun)
.TE
-
+.PP
The signals
.B SIGKILL
and
.B SIGSTOP
cannot be caught, blocked, or ignored.
-
-Next the signals not in the POSIX.1-1990 standard but described in
-SUSv2 and POSIX.1-2001.
-.TS
-l c c l
-____
-lB c c l.
-Signal Value Action Comment
-SIGBUS 10,7,10 Core Bus error (bad memory access)
-SIGPOLL Term Pollable event (Sys V).
- Synonym for \fBSIGIO\fP
-SIGPROF 27,27,29 Term Profiling timer expired
-SIGSYS 12,\-,12 Core Bad argument to routine (SVr4)
-SIGTRAP 5 Core Trace/breakpoint trap
-SIGURG 16,23,21 Ign Urgent condition on socket (4.2BSD)
-SIGVTALRM 26,26,28 Term Virtual alarm clock (4.2BSD)
-SIGXCPU 24,24,30 Core CPU time limit exceeded (4.2BSD)
-SIGXFSZ 25,25,31 Core File size limit exceeded (4.2BSD)
-.TE
-
+.PP
Up to and including Linux 2.2, the default behavior for
.BR SIGSYS ", " SIGXCPU ", " SIGXFSZ ", "
and (on architectures other than SPARC and MIPS)
.B SIGBUS
was to terminate the process (without a core dump).
-(On some other Unix systems the default action for
+(On some other UNIX systems the default action for
.BR SIGXCPU " and " SIGXFSZ
is to terminate the process without a core dump.)
Linux 2.4 conforms to the POSIX.1-2001 requirements for these signals,
terminating the process with a core dump.
-
-Next various other signals.
-.TS
-l c c l
-____
-lB c c l.
-Signal Value Action Comment
-SIGIOT 6 Core IOT trap. A synonym for \fBSIGABRT\fP
-SIGEMT 7,\-,7 Term
-SIGSTKFLT \-,16,\- Term Stack fault on coprocessor (unused)
-SIGIO 23,29,22 Term I/O now possible (4.2BSD)
-SIGCLD \-,\-,18 Ign A synonym for \fBSIGCHLD\fP
-SIGPWR 29,30,19 Term Power failure (System V)
-SIGINFO 29,\-,\- A synonym for \fBSIGPWR\fP
-SIGLOST \-,\-,\- Term File lock lost
-SIGWINCH 28,28,20 Ign Window resize signal (4.3BSD, Sun)
-SIGUNUSED \-,31,\- Term Unused signal (will be \fBSIGSYS\fP)
-.TE
-
-(Signal 29 is
-.B SIGINFO
-/
-.B SIGPWR
-on an alpha but
-.B SIGLOST
-on a sparc.)
-
+.PP
+.PP
.B SIGEMT
is not specified in POSIX.1-2001, but nevertheless appears
-on most other Unix systems,
+on most other UNIX systems,
where its default action is typically to terminate
the process with a core dump.
-
+.PP
.B SIGPWR
(which is not specified in POSIX.1-2001) is typically ignored
-by default on those other Unix systems where it appears.
-
+by default on those other UNIX systems where it appears.
+.PP
.B SIGIO
(which is not specified in POSIX.1-2001) is ignored by default
-on several other Unix systems.
-.SS "Real-time Signals"
+on several other UNIX systems.
+.\"
+.SS Signal numbering for standard signals
+The numeric value for each signal is given in the table below.
+As shown in the table, many signals have different numeric values
+on different architectures.
+The first numeric value in each table row shows the signal number
+on x86, ARM, and most other architectures;
+the second value is for Alpha and SPARC; the third is for MIPS;
+and the last is for PARISC.
+A dash (\-) denotes that a signal is absent on the corresponding architecture.
+.TS
+l c c c c l
+l c c c c l
+______
+lB c c c c l.
+Signal x86/ARM Alpha/ MIPS PARISC Notes
+ most others SPARC
+SIGHUP \01 \01 \01 \01
+SIGINT \02 \02 \02 \02
+SIGQUIT \03 \03 \03 \03
+SIGILL \04 \04 \04 \04
+SIGTRAP \05 \05 \05 \05
+SIGABRT \06 \06 \06 \06
+SIGIOT \06 \06 \06 \06
+SIGBUS \07 10 10 10
+SIGEMT \- \07 \07 -
+SIGFPE \08 \08 \08 \08
+SIGKILL \09 \09 \09 \09
+SIGUSR1 10 30 16 16
+SIGSEGV 11 11 11 11
+SIGUSR2 12 31 17 17
+SIGPIPE 13 13 13 13
+SIGALRM 14 14 14 14
+SIGTERM 15 15 15 15
+SIGSTKFLT 16 \- \- \07
+SIGCHLD 17 20 18 18
+SIGCLD \- \- 18 \-
+SIGCONT 18 19 25 26
+SIGSTOP 19 17 23 24
+SIGTSTP 20 18 24 25
+SIGTTIN 21 21 26 27
+SIGTTOU 22 22 27 28
+SIGURG 23 16 21 29
+SIGXCPU 24 24 30 12
+SIGXFSZ 25 25 31 30
+SIGVTALRM 26 26 28 20
+SIGPROF 27 27 29 21
+SIGWINCH 28 28 20 23
+SIGIO 29 23 22 22
+SIGPOLL Same as SIGIO
+SIGPWR 30 29/\- 19 19
+SIGINFO \- 29/\- \- \-
+SIGLOST \- \-/29 \- \-
+SIGSYS 31 12 12 31
+SIGUNUSED 31 \- \- 31
+.TE
+.PP
+Note the following:
+.IP * 3
+Where defined,
+.B SIGUNUSED
+is synonymous with
+.BR SIGSYS .
+Since glibc 2.26,
+.B SIGUNUSED
+is no longer defined on any architecture.
+.IP *
+Signal 29 is
+.BR SIGINFO / SIGPWR
+(synonyms for the same value) on Alpha but
+.B SIGLOST
+on SPARC.
+.\"
+.SS Real-time signals
+Starting with version 2.2,
Linux supports real-time signals as originally defined in the POSIX.1b
real-time extensions (and now included in POSIX.1-2001).
The range of supported real-time signals is defined by the macros
.B _POSIX_RTSIG_MAX
(8) real-time signals.
.PP
-The Linux kernel supports a range of 32 different real-time
-signals, numbered 33 to 64.
+The Linux kernel supports a range of 33 different real-time
+signals, numbered 32 to 64.
However, the glibc POSIX threads implementation internally uses
two (for NPTL) or three (for LinuxThreads) real-time signals
(see
Because the range of available real-time signals varies according
to the glibc threading implementation (and this variation can occur
at run time according to the available kernel and glibc),
-and indeed the range of real-time signals varies across Unix systems,
+and indeed the range of real-time signals varies across UNIX systems,
programs should
.IR "never refer to real-time signals using hard-coded numbers" ,
but instead should always refer to real-time signals using the notation
Unlike standard signals, real-time signals have no predefined meanings:
the entire set of real-time signals can be used for application-defined
purposes.
-(Note, however, that the LinuxThreads implementation uses the first
-three real-time signals.)
.PP
The default action for an unhandled real-time signal is to terminate the
receiving process.
while that signal is currently blocked, then only one instance is queued.
.IP 2. 4
If the signal is sent using
-.BR sigqueue (2),
+.BR sigqueue (3),
an accompanying value (either an integer or a pointer) can be sent
with the signal.
If the receiving process establishes a handler for this signal using the
.B SA_SIGINFO
flag to
-.BR sigaction (2)
+.BR sigaction (2),
then it can obtain this data via the
.I si_value
field of the
signals; see
.BR setrlimit (2)
for further details.
-.SS "Async-signal-safe functions"
.PP
-A signal handling routine established by
-.BR sigaction (2)
-or
-.BR signal (2)
-must be very careful, since processing elsewhere may be interrupted
-at some arbitrary point in the execution of the program.
-POSIX has the concept of "safe function".
-If a signal interrupts the execution of an unsafe function, and
-.I handler
-calls an unsafe function, then the behavior of the program is undefined.
-
-POSIX.1-2004 (also known as POSIX.1-2001 Technical Corrigendum 2)
-requires an implementation to guarantee that the following
-functions can be safely called inside a signal handler:
-.\" FIXME . SUSv4 adds functions to this list, and removes a few.
-
-.in +4
-.nf
-_Exit()
-_exit()
-abort()
-accept()
-access()
-aio_error()
-aio_return()
-aio_suspend()
-alarm()
-bind()
-cfgetispeed()
-cfgetospeed()
-cfsetispeed()
-cfsetospeed()
-chdir()
-chmod()
-chown()
-clock_gettime()
-close()
-connect()
-creat()
-dup()
-dup2()
-execle()
-execve()
-fchmod()
-fchown()
-fcntl()
-fdatasync()
-fork()
-fpathconf()
-fstat()
-fsync()
-ftruncate()
-getegid()
-geteuid()
-getgid()
-getgroups()
-getpeername()
-getpgrp()
-getpid()
-getppid()
-getsockname()
-getsockopt()
-getuid()
-kill()
-link()
-listen()
-lseek()
-lstat()
-mkdir()
-mkfifo()
-open()
-pathconf()
-pause()
-pipe()
-poll()
-posix_trace_event()
-pselect()
-raise()
-read()
-readlink()
-recv()
-recvfrom()
-recvmsg()
-rename()
-rmdir()
-select()
-sem_post()
-send()
-sendmsg()
-sendto()
-setgid()
-setpgid()
-setsid()
-setsockopt()
-setuid()
-shutdown()
-sigaction()
-sigaddset()
-sigdelset()
-sigemptyset()
-sigfillset()
-sigismember()
-signal()
-sigpause()
-sigpending()
-sigprocmask()
-sigqueue()
-sigset()
-sigsuspend()
-sleep()
-sockatmark()
-socket()
-socketpair()
-stat()
-symlink()
-sysconf()
-tcdrain()
-tcflow()
-tcflush()
-tcgetattr()
-tcgetpgrp()
-tcsendbreak()
-tcsetattr()
-tcsetpgrp()
-time()
-timer_getoverrun()
-timer_gettime()
-timer_settime()
-times()
-umask()
-uname()
-unlink()
-utime()
-wait()
-waitpid()
-write()
-.fi
-.in
-.SS Interruption of System Calls and Library Functions by Signal Handlers
+The addition of real-time signals required the widening
+of the signal set structure
+.RI ( sigset_t )
+from 32 to 64 bits.
+Consequently, various system calls were superseded by new system calls
+that supported the larger signal sets.
+The old and new system calls are as follows:
+.TS
+lb lb
+l l.
+Linux 2.0 and earlier Linux 2.2 and later
+\fBsigaction\fP(2) \fBrt_sigaction\fP(2)
+\fBsigpending\fP(2) \fBrt_sigpending\fP(2)
+\fBsigprocmask\fP(2) \fBrt_sigprocmask\fP(2)
+\fBsigreturn\fP(2) \fBrt_sigreturn\fP(2)
+\fBsigsuspend\fP(2) \fBrt_sigsuspend\fP(2)
+\fBsigtimedwait\fP(2) \fBrt_sigtimedwait\fP(2)
+.TE
+.\"
+.SS Interruption of system calls and library functions by signal handlers
If a signal handler is invoked while a system call or library
function call is blocked, then either:
.IP * 2
.BR SA_RESTART
flag (see
.BR sigaction (2)).
-The details vary across Unix systems;
+The details vary across UNIX systems;
below, the details for Linux.
-
+.PP
If a blocked call to one of the following interfaces is interrupted
-by a signal handler, then the call will be automatically restarted
+by a signal handler, then the call is automatically restarted
after the signal handler returns if the
.BR SA_RESTART
-flag was used; otherwise the call will fail with the error
+flag was used; otherwise the call fails with the error
.BR EINTR :
.\" The following system calls use ERESTARTSYS,
.\" so that they are restartable
-.RS 4
.IP * 2
.BR read (2),
.BR readv (2),
calls on "slow" devices.
A "slow" device is one where the I/O call may block for an
indefinite time, for example, a terminal, pipe, or socket.
-(A disk is not a slow device according to this definition.)
If an I/O call on a slow device has already transferred some
data by the time it is interrupted by a signal handler,
then the call will return a success status
(normally, the number of bytes transferred).
+Note that a (local) disk is not a slow device according to this definition;
+I/O operations on disk devices are not interrupted by signals.
.IP *
.BR open (2),
if it can block (e.g., when opening a FIFO; see
.BR connect (2),
.BR recv (2),
.BR recvfrom (2),
+.BR recvmmsg (2),
.BR recvmsg (2),
.BR send (2),
.BR sendto (2),
and
-.BR sendmsg (2).
+.BR sendmsg (2),
+.\" FIXME What about sendmmsg()?
+unless a timeout has been set on the socket (see below).
.IP *
File locking interfaces:
.BR flock (2)
and
+the
+.BR F_SETLKW
+and
+.BR F_OFD_SETLKW
+operations of
.BR fcntl (2)
-.BR F_SETLKW .
.IP *
POSIX message queue interfaces:
.BR mq_receive (3),
.IP *
.BR futex (2)
.B FUTEX_WAIT
-(since Linux 2.6.22; beforehand, always failed with
+(since Linux 2.6.22;
+.\" commit 72c1bbf308c75a136803d2d76d0e18258be14c7a
+beforehand, always failed with
.BR EINTR ).
.IP *
+.BR getrandom (2).
+.IP *
+.BR pthread_mutex_lock (3),
+.BR pthread_cond_wait (3),
+and related APIs.
+.IP *
+.BR futex (2)
+.BR FUTEX_WAIT_BITSET .
+.IP *
POSIX semaphore interfaces:
.BR sem_wait (3)
and
.BR sem_timedwait (3)
-(since Linux 2.6.22; beforehand, always failed with
+(since Linux 2.6.22;
+.\" as a consequence of the 2.6.22 changes in the futex() implementation
+beforehand, always failed with
+.BR EINTR ).
+.IP *
+.BR read (2)
+from an
+.BR inotify (7)
+file descriptor
+(since Linux 3.8;
+.\" commit 1ca39ab9d21ac93f94b9e3eb364ea9a5cf2aba06
+beforehand, always failed with
.BR EINTR ).
-.RE
.PP
The following interfaces are never restarted after
being interrupted by a signal handler,
when interrupted by a signal handler:
.\" These are the system calls that give EINTR or ERESTARTNOHAND
.\" on interruption by a signal handler.
-.RS 4
.IP * 2
+"Input" socket interfaces, when a timeout
+.RB ( SO_RCVTIMEO )
+has been set on the socket using
+.BR setsockopt (2):
+.BR accept (2),
+.BR recv (2),
+.BR recvfrom (2),
+.BR recvmmsg (2)
+(also with a non-NULL
+.IR timeout
+argument),
+and
+.BR recvmsg (2).
+.IP *
+"Output" socket interfaces, when a timeout
+.RB ( SO_RCVTIMEO )
+has been set on the socket using
+.BR setsockopt (2):
+.BR connect (2),
+.BR send (2),
+.BR sendto (2),
+and
+.BR sendmsg (2).
+.\" FIXME What about sendmmsg()?
+.IP *
Interfaces used to wait for signals:
.BR pause (2),
.BR sigsuspend (2),
and
.BR usleep (3).
.IP *
-.BR read (2)
-from an
-.BR inotify (7)
-file descriptor.
-.IP *
.BR io_getevents (2).
-.RE
.PP
The
.BR sleep (3)
function is also never restarted if interrupted by a handler,
but gives a success return: the number of seconds remaining to sleep.
-.SS Interruption of System Calls and Library Functions by Stop Signals
+.SS Interruption of system calls and library functions by stop signals
On Linux, even in the absence of signal handlers,
certain blocking interfaces can fail with the error
.BR EINTR
.BR SIGCONT .
This behavior is not sanctioned by POSIX.1, and doesn't occur
on other systems.
-
+.PP
The Linux interfaces that display this behavior are:
-.RS 4
+.IP * 2
+"Input" socket interfaces, when a timeout
+.RB ( SO_RCVTIMEO )
+has been set on the socket using
+.BR setsockopt (2):
+.BR accept (2),
+.BR recv (2),
+.BR recvfrom (2),
+.BR recvmmsg (2)
+(also with a non-NULL
+.IR timeout
+argument),
+and
+.BR recvmsg (2).
+.IP *
+"Output" socket interfaces, when a timeout
+.RB ( SO_RCVTIMEO )
+has been set on the socket using
+.BR setsockopt (2):
+.BR connect (2),
+.BR send (2),
+.BR sendto (2),
+and
+.\" FIXME What about sendmmsg()?
+.BR sendmsg (2),
+if a send timeout
+.RB ( SO_SNDTIMEO )
+has been set.
.IP * 2
.BR epoll_wait (2),
.BR epoll_pwait (2).
.BR sigtimedwait (2),
.BR sigwaitinfo (2).
.IP *
+Linux 3.7 and earlier:
.BR read (2)
from an
.BR inotify (7)
-file descriptor.
+file descriptor
+.\" commit 1ca39ab9d21ac93f94b9e3eb364ea9a5cf2aba06
.IP *
Linux 2.6.21 and earlier:
.BR futex (2)
.IP *
Linux 2.4 and earlier:
.BR nanosleep (2).
-.RE
-.SH "CONFORMING TO"
+.SH CONFORMING TO
POSIX.1, except as noted.
-.SH BUGS
-.B SIGIO
-and
-.B SIGLOST
-have the same value.
-The latter is commented out in the kernel source, but
-the build process of some software still thinks that
-signal 29 is
-.BR SIGLOST .
-.SH "SEE ALSO"
+.\" It must be a *very* long time since this was true:
+.\" .SH BUGS
+.\" .B SIGIO
+.\" and
+.\" .B SIGLOST
+.\" have the same value.
+.\" The latter is commented out in the kernel source, but
+.\" the build process of some software still thinks that
+.\" signal 29 is
+.\" .BR SIGLOST .
+.SH NOTES
+For a discussion of async-signal-safe functions, see
+.BR signal-safety (7).
+.SH SEE ALSO
.BR kill (1),
+.BR clone (2),
.BR getrlimit (2),
.BR kill (2),
-.BR killpg (2),
+.BR restart_syscall (2),
+.BR rt_sigqueueinfo (2),
.BR setitimer (2),
.BR setrlimit (2),
.BR sgetmask (2),
.BR signalfd (2),
.BR sigpending (2),
.BR sigprocmask (2),
-.BR sigqueue (2),
+.BR sigreturn (2),
.BR sigsuspend (2),
.BR sigwaitinfo (2),
.BR abort (3),
.BR bsd_signal (3),
+.BR killpg (3),
.BR longjmp (3),
+.BR pthread_sigqueue (3),
.BR raise (3),
+.BR sigqueue (3),
.BR sigset (3),
.BR sigsetops (3),
.BR sigvec (3),
.BR sysv_signal (3),
.BR core (5),
.BR proc (5),
-.BR pthreads (7)
+.BR nptl (7),
+.BR pthreads (7),
+.BR sigevent (7)
projects / thirdparty / man-pages.git / blobdiff