Re: [PATCH] Properly handle short writes in sigint handlers

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+From: Tomi Ollila <tomi.ollila@iki.fi>\r
+To: David Edmondson <dme@dme.org>, Austin Clements <amdragon@MIT.EDU>,\r
+       notmuch@notmuchmail.org\r
+Subject: Re: [PATCH] Properly handle short writes in sigint handlers\r
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+Date: Fri, 23 Dec 2011 14:30:50 +0200\r
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+\r
+On Fri, 23 Dec 2011 08:10:33 +0000, David Edmondson <dme@dme.org> wrote:\r
+> Sorry for being slow.\r
+> \r
+> Can you describe the situation in which you expect a write to stderr to\r
+> be a short write? (Without error.)\r
+\r
+In the following hypothetical case (correct me if I'm wrong :):\r
+\r
+* There is 4096 byte buffer in tty driver.\r
+* Stderr is in blocking-mode (the usual case).\r
+* There is already 4090 bytes in that buffer that has not been read.\r
+* One attemtps to write "Stopping...         \n" there (blocks).\r
+* Somehow the system call is interrupted (and SA_RESTART not set)\r
+  -- write() should return 6 bytes written.\r
+\r
+But, if the buffer is full already, does the write() system call return\r
+with -1 and EINTR set ?\r
+\r
+If there is enough space for all data in that buffer to begin with, \r
+write() should be atomic.\r
+\r
+> In that situation, what guarantee is there that the loop you've written\r
+> will terminate?\r
+\r
+If write() keeps returning 0 then it will not terminate (I guess this never\r
+happens). Also, it never terminates if write blocks indefinitely \r
+(with or without that loop).\r
+\r
+> We're not talking about safeguarding a users' data here - this is a\r
+> short message to indicate that a tool is terminating due to a signal.\r
+> I'm concerned that the solution is worse than the problem.\r
+\r
+I'm also in favor of "opportunistic" write *in this particular case*\r
+\r
+In case that write fails there is most probably more serious things going\r
+on (all resources eaten, hardware problem, etc) and trying to push these\r
+writes forward doesn't help.\r
+\r
+Tomi\r