https://bugs.freedesktop.org/show_bug.cgi?id=82290
Priority: medium
Bug ID: 82290
Assignee: libreoffice-bugs@lists.freedesktop.org
Summary: EPS rendering using GS may cause pipe writing deadlock
Severity: major
Classification: Unclassified
OS: Linux (All)
Reporter: hiroto.kagot...@gmail.com
Hardware: All
Status: UNCONFIRMED
Version: 4.2.5.2 release
Component: filters and storage
Product: LibreOffice
If I have pstoedit, there is no problem with handling EPS files. Without
pstoedit, EPS is rendered as BMP using GS in RenderAsBMPThroughHelper(). The
input/output to/from GS are transferred using pipes.
RenderAsBMPThroughHelper() first writes the EPS file content to a pipe pIn,
then closes the pipe, and then reads BMP result from another pipe pOut. With
this sequence, GS may start to produce the BMP result as soon as it reads a
"showpage" operator from stdin, and this causes a deadlock between LO writing
to a pipe and GS writing to another pipe.
On FreeBSD, this situation frequently happens because write(2) >= 8KB to pipes
always blocks until the whole pipe buffer content is consumed by read(2).
On Linux, this situation rarely happens because write(2) to pipes returns
immediately if the size is less than the buffer size. However, large EPS using
a "showpage" operator and including a large bogus trailer can cause this
deadlock. Attached EPS and ODP are example files that cause the deadlock.
How-to-repeat:
Make sure pstoedit is NOT installed and GS is properly installed.
On FreeBSD (9.3R or 10.0R) or Linux (Fedora 20), open the attached ODP file, or
insert the attached EPS file to any LO document.
Fix:
There are several solutions to fix this deadlock.
1. Do not use pipes for both direction. Like in RenderAsEMF(), use a temporary
file for BMP result.
2. Do not use blocking write(2)/read(2). Make them non-blocking, and use
select(2) to choose the next operation.
3. Perform write(2) and read(2) concurrently. Create a new thread and perform
write(2) in it.
Attached patch is for the 3rd solution.
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