Read Error Interrupted System Call
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Interrupted System Call Linux
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Interrupted System Call Select
each other. Join them; it only takes a minute: Sign up How to handle EINTR (interrupted System Call) up vote 3 down vote favorite 3 My user-space application sometimes blocks after receiving an EINTR-Signal, somehow. What I recorded with strace: time(NULL) = 1257343042 time(NULL) = 1257343042 rt_sigreturn(0xbff07be4) = -1 EINTR (Interrupted system call) --- SIGALRM (Alarm clock) @
Top: Failed Tty Set:
0 (0) --- time(NULL) = 1257343042 futex(0xb7cea80c, 0x80 /* FUTEX_??? */, 2) = ? ERESTARTSYS (To be restarted) --- SIGUSR1 (User defined signal 1) @ 0 (0) --- sigreturn() = ? (mask now [ALRM]) futex(0xb7cea80c, 0x80 /* FUTEX_??? */, 2) = ? ERESTARTSYS (To be restarted) --- SIGWINCH (Window changed) @ 0 (0) --- futex(0xb7cea80c, 0x80 /* FUTEX_??? */, 2) = ? ERESTARTSYS (To be restarted) --- SIGTERM (Terminated) @ 0 (0) --- time(NULL) = 1257343443 time(NULL) = 1257343443 futex(0xb7cea80c, 0x80 /* FUTEX_??? */, 2) = ? ERESTARTSYS (To be restarted) --- SIGWINCH (Window changed) @ 0 (0) --- futex(0xb7cea80c, 0x80 /* FUTEX_??? */, 2 Can I catch the EINTR signal and how can I repeat concerned calls such as write, read or select? How can I determine WHERE this EINTR occurred, even if I used third-party libraries working with system calls? Why my app is completely blocked after receiving an EINTR (see strace dump: I sent a SIGUSR1 which normally should be handled)? And why is futex() returning ERESTARTSYS t
errno was set to EINTR. This was done under the assumption that since a signal occurred and the process caught it, there is a good chance that something has happened that should interrupted system call (code=4) wake up the blocked system call. Here, we have to differentiate between a system
Poll Eintr
call and a function. It is a system call within the kernel that is interrupted when a signal is caught. To support select eintr this feature, the system calls are divided into two categories: the "slow" system calls and all the others. The slow system calls are those that can block forever. Included in this category are Reads that http://stackoverflow.com/questions/1674162/how-to-handle-eintr-interrupted-system-call can block the caller forever if data isn't present with certain file types (pipes, terminal devices, and network devices)Writes that can block the caller forever if the data can't be accepted immediately by these same file typesOpens that block until some condition occurs on certain file types (such as an open of a terminal device that waits until an attached modem answers the phone)The pause function (which by definition puts the calling http://poincare.matf.bg.ac.rs/~ivana/courses/tos/sistemi_knjige/pomocno/apue/APUE/0201433079/ch10lev1sec5.html process to sleep until a signal is caught) and the wait functionCertain ioctl operationsSome of the interprocess communication functions (Chapter 15) The notable exception to these slow system calls is anything related to disk I/O. Although a read or a write of a disk file can block the caller temporarily (while the disk driver queues the request and then the request is executed), unless a hardware error occurs, the I/O operation always returns and unblocks the caller quickly. One condition that is handled by interrupted system calls, for example, is when a process initiates a read from a terminal device and the user at the terminal walks away from the terminal for an extended period. In this example, the process could be blocked for hours or days and would remain so unless the system was taken down. POSIX.1 semantics for interrupted reads and writes changed with the 2001 version of the standard. Earlier versions gave implementations a choice for how to deal with reads and writes that have processed partial amounts of data. If read has received and transferred data to an application's buffer, but has not yet received all that the application requested and is then interrupted, the operating system could either fail the system call with errno set to E
point about the behavior of the Unix (socket API) connect() system call when it is interrupted by a signal. It points out how obscure the Single Unix http://www.madore.org/~david/computers/connect-intr.html Specification is, and notes that many existing Unix implementations seem to have f*cked this up somehow. The question is this: if a blocking connect() (on a blocking stream https://books.google.gr/books?id=ptSC4LpwGA0C&pg=PA134&lpg=PA134&dq=read+error+interrupted+system+call&source=bl&ots=Ks7ELggnSq&sig=9Y0JM5qDVmZUSBcPUoqj2_XOvZk&hl=en&sa=X&ved=0ahUKEwiVnbmhxurPAhWBkywKHbsdBWEQ6AEIWzAI socket, that is) is interrupted by a signal, returning EINTR, in what state is the socket left, and is it permissible to restart the system call? What happens if interrupted system a second connect() with the same arguments is attempted immediately after one failed with EINTR? The reference for connect() (hereafter, “the Spec”) is part of the Open Group's Single Unix Specification, version3 (note: you may need to register to read this; see also here). Here is the relevant part of it: If the initiating socket is connection-mode, then interrupted system call connect() shall attempt to establish a connection to the address specified by the address argument. If the connection cannot be established immediately and O_NONBLOCK is not set for the file descriptor for the socket, connect() shall block for up to an unspecified timeout interval until the connection is established. If the timeout interval expires before the connection is established, connect() shall fail and the connection attempt shall be aborted. If connect() is interrupted by a signal that is caught while blocked waiting to establish a connection, connect() shall fail and set connect() to [EINTR], but the connection request shall not be aborted, and the connection shall be established asynchronously. If the connection cannot be established immediately and O_NONBLOCK is set for the file descriptor for the socket, connect() shall fail and set errno to [EINPROGRESS], but the connection request shall not be aborted, and the connection shall be established asynchronously. Subsequent calls to connect() for the same socket, before the connection is established, shall fail and set errno to [EALREADY]. Wh
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