[crashtracker] Prevent crashtracker from deadlocking #1111
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BenchmarksComparisonBenchmark execution time: 2025-06-17 08:10:03 Comparing candidate commit 8eb0506 in PR branch Found 0 performance improvements and 0 performance regressions! Performance is the same for 52 metrics, 2 unstable metrics. CandidateCandidate benchmark detailsGroup 1
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BaselineOmitted due to size. |
bwoebi
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Jun 17, 2025
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Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #1111 +/- ##
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+ Coverage 70.97% 71.00% +0.03%
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Files 336 336
Lines 51191 51194 +3
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+ Hits 36332 36350 +18
+ Misses 14859 14844 -15
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Artifact Size Benchmark Reportaarch64-alpine-linux-musl
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Yeah, I did not want to make the complex more complex directly. Generally
maybe, it was to take care of the case where the file is big. I can make it 4k if you think it would be safer. |
danielsn
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Jun 25, 2025
| // This function may run in signal handler, so we should ensure that we do not allocate | ||
| // memory on the heap (ex: avoiding using BufReader for exao). | ||
| let mut file = File::open("/proc/self/status")?; | ||
| let mut buf = [0u8; 8192]; |
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how long do we expect the file to be, worst case?
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in general it's less than 4KB, a pathological case would be 8-10KB but I've never seen such thing
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would there be value in looping if there are still bytes left?
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TBH I do not know, my main goal is to avoid calling malloc here as simple as I can.
going for looping would make thing more complex and we sufficient space, I feel like it won't be necessary.
WDYT ?
| let data = &buf[..n]; | ||
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| for line in data.split(|&b| b == b'\n') { | ||
| if let Ok(line_str) = std::str::from_utf8(line) { |
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IF this fails, should we return false, or an error?
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The question would be what should we do on error.
Today, the semantic is:
Ok(true): useCLONE_PTRACEas an extra-flagsOk(false): use0to specify no clone flags
Should an error have the same behavior as Ok(false) or should be stop and no crash report is generated ?
All that said, I would say, we are fine today :)
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I would continue. Best effort is all we can do.
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so keep it like that
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Is there a specific reason this hasn't been merged yet? @gleocadie |
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What does this PR do?
Prevent crashtracker from deadlocking when calling
is_being_tracedfunction.Motivation
We got a recent report with this callstack (shorten):
As you can see, an allocation is done while running in the signal handler. As shown in this case, this causes a deadlock: application gets stuck.
This happens (as seen in the callstack),
BufReader::newallocates. This is done here.To avoid that, we need a zero-heap-allocation version of this version.