OK, I managed to create an example without callr, but it is still somewhat cumbersome. Anyway, here it is. Terminal 1: mkfifo fif R --no-readline --slave --no-save --no-restore < fif Terminal 2: cat > fif Sys.getpid() This will make Terminal 1 print the pid of the R process, so we can send a SIGINT: Terminal 3: kill -INT pid The R process is of course still running happily. Terminal 2 again: tryCatch(Sys.sleep(10), interrupt = function(e) e) and then Terminal 1 prints the interrupt condition: <interrupt: > This is macOS and 3.5.3, although I don't think it matters much. Thanks much! G. On Tue, Apr 30, 2019 at 9:50 PM Simon Urbanek <simon.urbanek at r-project.org> wrote:> > Can you give an example without callr? The key is how is the process stated and what it is doing which is entirely opaque in callr. > > Windows doesn't have signals, so the process there is entirely different. Most of the WIN32 processing is event-based. > > Cheers, > Simon > > > > On Apr 30, 2019, at 4:17 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote: > > > > Yeah, I get that they are async. > > > > What happens is that the background process is not doing anything when > > the process gets a SIGINT. I.e. the background process is just > > listening on its standard input. > > > > AFAICT for an interactive process such a SIGINT is just swallowed, > > with a newline outputted to the terminal. > > > > But apparently, for this background process, it is not swallowed, and > > it is triggered later. FWIW it does not happen on Windows, not very > > surprisingly. > > > > Gabor > > > > On Tue, Apr 30, 2019 at 9:13 PM Simon Urbanek > > <simon.urbanek at r-project.org> wrote: > >> > >> Interrupts are not synchronous in R - the signal only flags the request for interruption. Nothing actually happens until R_CheckUserInterrupt() is called at an interruptible point. In you case your code is apparently not calling R_CheckUserInterrupt() until later as a side-effect of the next evaluation. > >> > >> Cheers, > >> Simon > >> > >> > >>> On Apr 30, 2019, at 3:44 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote: > >>> > >>> Hi All, > >>> > >>> I realize that this is not a really nice reprex, but anyone has an > >>> idea why a background R session would "remember" an interrupt (SIGINT) > >>> on Unix? > >>> > >>> rs <- callr::r_session$new() > >>> rs$interrupt() # just sends a SIGINT > >>> #> [1] TRUE > >>> > >>> rs$run(function() 1+1) > >>> #> Error: interrupt > >>> > >>> rs$run(function() 1+1) > >>> #> [1] 2 > >>> > >>> It seems that the main loop somehow stores the SIGINT it receives > >>> while it is waiting on stdin, and then it triggers it when some input > >>> comes in.... Maybe. Just speculating.... > >>> > >>> Thanks, > >>> Gabor > >>> > >>> ______________________________________________ > >>> R-devel at r-project.org mailing list > >>> https://stat.ethz.ch/mailman/listinfo/r-devel > >>> > >> > > >
Tierney, Luke
2019-Apr-30 21:55 UTC
[Rd] [External] Re: Background R session on Unix and SIGINT
A Simon pointed out the interrupt is recorded but not processed until a safe point. When reading from a fifo or pipe R runs non-interactive, which means is sits in a read() system call and the interrupt isn't seen until sometime during evaluation when a safe checkpoint is reached. When reading from a terminal R will use select() to wait for input and periodically wake and check for interrupts. In that case the interrupt will probably be seen sooner. If the interactive behavior is what you want you can add --interactive to the arguments used to start R. Best, luke On Tue, 30 Apr 2019, G?bor Cs?rdi wrote:> OK, I managed to create an example without callr, but it is still > somewhat cumbersome. Anyway, here it is. > > Terminal 1: > mkfifo fif > R --no-readline --slave --no-save --no-restore < fif > > Terminal 2: > cat > fif > Sys.getpid() > > This will make Terminal 1 print the pid of the R process, so we can > send a SIGINT: > > Terminal 3: > kill -INT pid > > The R process is of course still running happily. > > Terminal 2 again: > tryCatch(Sys.sleep(10), interrupt = function(e) e) > > and then Terminal 1 prints the interrupt condition: > <interrupt: > > > This is macOS and 3.5.3, although I don't think it matters much. > > Thanks much! > G. > > On Tue, Apr 30, 2019 at 9:50 PM Simon Urbanek > <simon.urbanek at r-project.org> wrote: >> >> Can you give an example without callr? The key is how is the process stated and what it is doing which is entirely opaque in callr. >> >> Windows doesn't have signals, so the process there is entirely different. Most of the WIN32 processing is event-based. >> >> Cheers, >> Simon >> >> >>> On Apr 30, 2019, at 4:17 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote: >>> >>> Yeah, I get that they are async. >>> >>> What happens is that the background process is not doing anything when >>> the process gets a SIGINT. I.e. the background process is just >>> listening on its standard input. >>> >>> AFAICT for an interactive process such a SIGINT is just swallowed, >>> with a newline outputted to the terminal. >>> >>> But apparently, for this background process, it is not swallowed, and >>> it is triggered later. FWIW it does not happen on Windows, not very >>> surprisingly. >>> >>> Gabor >>> >>> On Tue, Apr 30, 2019 at 9:13 PM Simon Urbanek >>> <simon.urbanek at r-project.org> wrote: >>>> >>>> Interrupts are not synchronous in R - the signal only flags the request for interruption. Nothing actually happens until R_CheckUserInterrupt() is called at an interruptible point. In you case your code is apparently not calling R_CheckUserInterrupt() until later as a side-effect of the next evaluation. >>>> >>>> Cheers, >>>> Simon >>>> >>>> >>>>> On Apr 30, 2019, at 3:44 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote: >>>>> >>>>> Hi All, >>>>> >>>>> I realize that this is not a really nice reprex, but anyone has an >>>>> idea why a background R session would "remember" an interrupt (SIGINT) >>>>> on Unix? >>>>> >>>>> rs <- callr::r_session$new() >>>>> rs$interrupt() # just sends a SIGINT >>>>> #> [1] TRUE >>>>> >>>>> rs$run(function() 1+1) >>>>> #> Error: interrupt >>>>> >>>>> rs$run(function() 1+1) >>>>> #> [1] 2 >>>>> >>>>> It seems that the main loop somehow stores the SIGINT it receives >>>>> while it is waiting on stdin, and then it triggers it when some input >>>>> comes in.... Maybe. Just speculating.... >>>>> >>>>> Thanks, >>>>> Gabor >>>>> >>>>> ______________________________________________ >>>>> R-devel at r-project.org mailing list >>>>> https://stat.ethz.ch/mailman/listinfo/r-devel >>>>> >>>> >>> >> > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >-- Luke Tierney Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics and Fax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: luke-tierney at uiowa.edu Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
Gábor Csárdi
2019-Apr-30 23:03 UTC
[Rd] [External] Re: Background R session on Unix and SIGINT
Unfortunately --interactive also makes the session interactive(), which is bad for me, as it is a background session. In general, I don't want the interactive behavior, but was wondering if I could send as SIGINT to try to interrupt the computation of the background process, and if that does not work, then I would send a SIGKILL and start up another process. It all works nicely, except for this glitch, but I think I can work around it. Thanks, Gabor On Tue, Apr 30, 2019 at 10:55 PM Tierney, Luke <luke-tierney at uiowa.edu> wrote:> > A Simon pointed out the interrupt is recorded but not processed until > a safe point. > > When reading from a fifo or pipe R runs non-interactive, which means > is sits in a read() system call and the interrupt isn't seen until > sometime during evaluation when a safe checkpoint is reached. > > When reading from a terminal R will use select() to wait for input and > periodically wake and check for interrupts. In that case the interrupt > will probably be seen sooner. > > If the interactive behavior is what you want you can add --interactive > to the arguments used to start R. > > Best, > > luke > > On Tue, 30 Apr 2019, G?bor Cs?rdi wrote: > > > OK, I managed to create an example without callr, but it is still > > somewhat cumbersome. Anyway, here it is. > > > > Terminal 1: > > mkfifo fif > > R --no-readline --slave --no-save --no-restore < fif > > > > Terminal 2: > > cat > fif > > Sys.getpid() > > > > This will make Terminal 1 print the pid of the R process, so we can > > send a SIGINT: > > > > Terminal 3: > > kill -INT pid > > > > The R process is of course still running happily. > > > > Terminal 2 again: > > tryCatch(Sys.sleep(10), interrupt = function(e) e) > > > > and then Terminal 1 prints the interrupt condition: > > <interrupt: > > > > > This is macOS and 3.5.3, although I don't think it matters much. > > > > Thanks much! > > G. > > > > On Tue, Apr 30, 2019 at 9:50 PM Simon Urbanek > > <simon.urbanek at r-project.org> wrote: > >> > >> Can you give an example without callr? The key is how is the process stated and what it is doing which is entirely opaque in callr. > >> > >> Windows doesn't have signals, so the process there is entirely different. Most of the WIN32 processing is event-based. > >> > >> Cheers, > >> Simon > >> > >> > >>> On Apr 30, 2019, at 4:17 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote: > >>> > >>> Yeah, I get that they are async. > >>> > >>> What happens is that the background process is not doing anything when > >>> the process gets a SIGINT. I.e. the background process is just > >>> listening on its standard input. > >>> > >>> AFAICT for an interactive process such a SIGINT is just swallowed, > >>> with a newline outputted to the terminal. > >>> > >>> But apparently, for this background process, it is not swallowed, and > >>> it is triggered later. FWIW it does not happen on Windows, not very > >>> surprisingly. > >>> > >>> Gabor > >>> > >>> On Tue, Apr 30, 2019 at 9:13 PM Simon Urbanek > >>> <simon.urbanek at r-project.org> wrote: > >>>> > >>>> Interrupts are not synchronous in R - the signal only flags the request for interruption. Nothing actually happens until R_CheckUserInterrupt() is called at an interruptible point. In you case your code is apparently not calling R_CheckUserInterrupt() until later as a side-effect of the next evaluation. > >>>> > >>>> Cheers, > >>>> Simon > >>>> > >>>> > >>>>> On Apr 30, 2019, at 3:44 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote: > >>>>> > >>>>> Hi All, > >>>>> > >>>>> I realize that this is not a really nice reprex, but anyone has an > >>>>> idea why a background R session would "remember" an interrupt (SIGINT) > >>>>> on Unix? > >>>>> > >>>>> rs <- callr::r_session$new() > >>>>> rs$interrupt() # just sends a SIGINT > >>>>> #> [1] TRUE > >>>>> > >>>>> rs$run(function() 1+1) > >>>>> #> Error: interrupt > >>>>> > >>>>> rs$run(function() 1+1) > >>>>> #> [1] 2 > >>>>> > >>>>> It seems that the main loop somehow stores the SIGINT it receives > >>>>> while it is waiting on stdin, and then it triggers it when some input > >>>>> comes in.... Maybe. Just speculating.... > >>>>> > >>>>> Thanks, > >>>>> Gabor > >>>>> > >>>>> ______________________________________________ > >>>>> R-devel at r-project.org mailing list > >>>>> https://stat.ethz.ch/mailman/listinfo/r-devel > >>>>> > >>>> > >>> > >> > > > > ______________________________________________ > > R-devel at r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > -- > Luke Tierney > Ralph E. Wareham Professor of Mathematical Sciences > University of Iowa Phone: 319-335-3386 > Department of Statistics and Fax: 319-335-3017 > Actuarial Science > 241 Schaeffer Hall email: luke-tierney at uiowa.edu > Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu