Date: Sat, 17 Oct 2009 19:55:55 +0200 From: Jilles Tjoelker <jilles@stack.nl> To: "Mikhail T." <mi+thun@aldan.algebra.com> Cc: Kostik Belousov <kostikbel@gmail.com>, stable@freebsd.org Subject: Re: Can close-ing a pipe trigger a SIGPIPE? Message-ID: <20091017175555.GA76378@stack.nl> In-Reply-To: <4ADA01C2.3000303@aldan.algebra.com> References: <4AD9F4ED.2050002@aldan.algebra.com> <20091017172718.GJ2160@deviant.kiev.zoral.com.ua> <4ADA01C2.3000303@aldan.algebra.com>
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On Sat, Oct 17, 2009 at 01:41:22PM -0400, Mikhail T. wrote: > Kostik Belousov wrote: > > Take ktrace of both parent and child. > Great idea! Here is the kdump's listing for both (after ktrace -i): > http://aldan.algebra.com/~mi/tmp/tclx-kdump.txt > (it is large, so be sure to use a compressing browser). Once loaded, > look for substring: > Error SIGPIPE signal received while closing file5. > The parent process-ID is 92722. The child -- 92723. Thanks! Yours, The interesting part of the ktrace: 92723 tclsh8.5 CALL exit(0) 92722 tclsh8.5 CALL sigaction(SIGPIPE,0x7fffffffa9e0,0) 92722 tclsh8.5 RET sigaction 0 92722 tclsh8.5 CALL write(0x4,0x800e24028,0) 92722 tclsh8.5 RET write -1 errno 32 Broken pipe 92722 tclsh8.5 PSIG SIGPIPE caught handler=0x800f126d0 mask=0x0 code=0x0 92722 tclsh8.5 CALL sigreturn(0x7fffffffa0c0) 92722 tclsh8.5 RET sigreturn JUSTRETURN 92722 tclsh8.5 CALL close(0x5) 92722 tclsh8.5 RET close 0 92722 tclsh8.5 CALL close(0x4) 92722 tclsh8.5 RET close 0 It seems unwise to assume that a write(2) of 0 bytes is a noop. Even if it is, doing it is a waste of a system call. -- Jilles Tjoelker
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