[crashtracker] Enable client to configure which signals to trap #856
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danielsn
commented
Feb 5, 2025
| SigHandler::Handler(f) => f(signum), | ||
| SigHandler::SigAction(f) => f(signum, sig_info, ucontext), | ||
| }; | ||
| eprintln!("Unexpected signal number {signum}, can't chain the handlers"); |
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What should we do here? abort?
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I guess this could happen if the user code changes the sigaction while we're in the middle of handling a signal? I'm not sure how it might arise.
danielsn
commented
Feb 5, 2025
| unsafe { create_alt_stack()? }; | ||
| } | ||
| let mut old_handlers = HashMap::new(); | ||
| // TODO: if this fails, we end in a situation where handlers have been registered with no chain |
danielsn
commented
Feb 5, 2025
| let boxed_ptr = Box::into_raw(Box::new(old_handlers)); | ||
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| let res = OLD_HANDLERS.compare_exchange(ptr::null_mut(), boxed_ptr, SeqCst, SeqCst); | ||
| anyhow::ensure!( |
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This leaks the old_handlers, if we care?
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I don't think so--small one-time leak, right?
danielsn
commented
Feb 5, 2025
| @@ -674,9 +665,11 @@ pub fn restore_old_handlers(inside_signal_handler: bool) -> anyhow::Result<()> { | |||
| anyhow::ensure!(!prev.is_null(), "No crashtracking previous signal handlers"); | |||
| // Safety: The only nonnull pointer stored here comes from Box::into_raw() | |||
| let prev = unsafe { Box::from_raw(prev) }; | |||
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We could flip this around, and only rehydrate into a box when we are ready to drop it
BenchmarksComparisonBenchmark execution time: 2025-02-12 17:57:05 Comparing candidate commit a6154dd 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. |
danielsn
commented
Feb 5, 2025
danielsn
commented
Feb 5, 2025
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danielsn
commented
Feb 6, 2025
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #856 +/- ##
==========================================
- Coverage 71.90% 71.67% -0.24%
==========================================
Files 324 324
Lines 48077 48226 +149
==========================================
- Hits 34572 34568 -4
- Misses 13505 13658 +153
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One thing I strongly recommend is: let's put in some defaults! In past features "leaving it up to implementer" often meant unintended inconsistency as things get picked semi-randomly; I think in general it's nice to have a pattern of "if you don't want to choose, we pick a reasonable default, don't worry about it". |
https://github.com/DataDog/libdatadog/pull/856/files#diff-fded76796d1b1945fd14d3cdb6230e4692e94608fc4887d26e2530a004df451aR59 |
Ahaha my bad for scrolling too fast through the PR, and amazing work in getting this in :D :D :D |
sanchda
approved these changes
Feb 10, 2025
| SigHandler::Handler(f) => f(signum), | ||
| SigHandler::SigAction(f) => f(signum, sig_info, ucontext), | ||
| }; | ||
| eprintln!("Unexpected signal number {signum}, can't chain the handlers"); |
There was a problem hiding this comment.
I guess this could happen if the user code changes the sigaction while we're in the middle of handling a signal? I'm not sure how it might arise.
| let boxed_ptr = Box::into_raw(Box::new(old_handlers)); | ||
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| let res = OLD_HANDLERS.compare_exchange(ptr::null_mut(), boxed_ptr, SeqCst, SeqCst); | ||
| anyhow::ensure!( |
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I don't think so--small one-time leak, right?
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What does this PR do?
Instead of hardcoding the signals to trap, allow the client to specify them
Motivation
We wanted to catch sigabort and sigill in addition to sigsegv and sigbus, and I figured lets just make it generic.
Additional Notes
Anything else we should know when reviewing?
How to test the change?