brew.sh: fix sporadic SIGPIPE in CPU feature check (Fixes #21365) #21366
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The previous implementation used a pipeline: grep -E "^(flags|Features)" /proc/cpuinfo | grep -q "ssse3" This caused a race condition. If the second grep (grep -q) found a match and exited early, it closed the read end of the pipe. If the first grep was still writing to that pipe (processing subsequent lines of /proc/cpuinfo), it would receive a SIGPIPE and print 'grep: write error: Broken pipe' to stderr. This patch consolidates the logic into a single grep command: grep -qE '^(flags|Features).*\bssse3\b' /proc/cpuinfo This eliminates the pipeline entirely, preventing the broken pipe error while maintaining the same logic: verifying that 'ssse3' appears on a line starting with 'flags' or 'Features'.
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Pull request overview
This PR fixes a race condition that caused sporadic SIGPIPE errors during CPU feature detection on Linux systems. The issue occurred when using a pipeline of two grep commands to check for SSSE3 CPU support.
Key Changes:
- Consolidated two piped grep commands into a single grep operation to eliminate the race condition
- Added word boundary anchors (
\b) to improve pattern matching precision
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@fourdollars Note for future reference you don't need to open an issue if you're going to open a PR to fix it; just open the PR. |
But I have followed this. I am confused. |
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@fourdollars Thanks for feedback, I will adjust. |
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@fourdollars Thanks, opened #21391 to clarify. |
Fixes #21365
Closes #21359
The previous implementation used a pipeline:
grep -E "^(flags|Features)" /proc/cpuinfo | grep -q "ssse3"
This caused a race condition. If the second grep (grep -q) found a match and exited early, it closed the read end of the pipe. If the first grep was still writing to that pipe (processing subsequent lines of /proc/cpuinfo), it would receive a SIGPIPE and print 'grep: write error: Broken pipe' to stderr.
This patch consolidates the logic into a single grep command:
grep -qE '^(flags|Features).*\bssse3\b' /proc/cpuinfo
This eliminates the pipeline entirely, preventing the broken pipe error while maintaining the same logic: verifying that 'ssse3' appears on a line starting with 'flags' or 'Features'.
brew lgtm(style, typechecking and tests) with your changes locally?