From e05b498065eaf49cc392b0315a26fe8f416b8ac1 Mon Sep 17 00:00:00 2001 From: Roman Divacky Date: Tue, 6 Oct 2009 20:19:16 +0000 Subject: [PATCH] Fix tcsh losing history when tcsh terminates because the pty beneath it is closed. Diagnosed by Ted Anderson: New signal queuing logic was introduced in 6.15 and allows the signal handlers to be run explicitly by calling handle_pending_signals, instead of immediately when the signal is delivered. This function is called at various places, typically when receiving a EINTR from a slow system call such as read or write. In the pty exit case, it was called from xwrite, called from flush, while printing the "exit" message after receiving EOF when reading from the pty (note that the read did not return EINTR but zero bytes, indicating EOF). The SIGHUP handler, phup(), called rechist, which opened the history file and began writing the merged history to it. This process invoked flush recursively to actually write the data. In this case, however, the flush noticed it was being called recursively and decided fail by calling stderror. My conclusion was that the signal was being handled at a bad time. But whether to fix flush not to care about the recursive call, or to handle the signal some other time and when to handle it, was unclear to me. However, by adding an extra call to handle_pending_signals, just after process() returns to main(), I was able to avoid the truncated history after network outages and similar failures. I verified this fix in version 6.17. Approved by: ed (mentor) MFC after: 1 week --- contrib/tcsh/sh.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/contrib/tcsh/sh.c b/contrib/tcsh/sh.c index 73b6d7f5483..f90eeab1942 100644 --- a/contrib/tcsh/sh.c +++ b/contrib/tcsh/sh.c @@ -1291,6 +1291,8 @@ main(int argc, char **argv) /* * Mop-up. */ + /* Take care of these (especially HUP) here instead of inside flush. */ + handle_pending_signals(); if (intty) { if (loginsh) { xprintf("logout\n");