Red Hat Bugzilla – Bug 49104
Buffered I/O calls not thread safe on multiprocessor systems
Last modified: 2008-05-01 11:38:00 EDT
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Description of problem:
When using buffered I/O calls (fopen, fread, fwrite, fclose) to read and
write files from multithreaded programs, data corruption occurs when run
on multiprocessor machine. The same program using non-buffered calls
(open, close, read, write) works fine.
Steps to Reproduce:
1. Build attached freadtest.cpp program using "g++ freadtest.cpp -o
2. Run freadtest
3. Build readtest.cpp program using "g++ readtest.cpp -o readtest -
lpthread" to see working version using non-buffered calls
Actual Results: In the buffered I/O version, around 3-5% of the time the
data gets corrupted.
Expected Results: In the non-buffered I/O version, the data is never
Created attachment 23547 [details]
Sample code to reproduce problem
Created attachment 23548 [details]
Sample code of working version using non-buffered calls
Cannot reproduce this (2way PIII). I was running /bin/true loop with this
for several hours without getting any corruption.