Fix process hang on /exit due to bubbletea renderer deadlock#2269
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dgageot merged 2 commits intodocker:mainfrom Mar 28, 2026
Merged
Fix process hang on /exit due to bubbletea renderer deadlock#2269dgageot merged 2 commits intodocker:mainfrom
dgageot merged 2 commits intodocker:mainfrom
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Add tests that demonstrate the bubbletea v2 renderer mutex deadlock that causes the process to hang after /exit when stdout blocks. - TestExitDeadlock_BlockedStdout: proves p.Run() hangs when the renderer's flush goroutine holds the mutex during a blocked stdout write, preventing the final render after tea.Quit. - TestExitSafetyNet_BlockedStdout: verifies a safety-net timer can break the deadlock by calling an exit function. - TestExitSafetyNet_GracefulShutdown: verifies the safety net does not fire during normal (non-blocked) shutdown. - TestCleanupAll_SpawnsSafetyNet: verifies cleanupAll spawns the safety-net goroutine that calls exitFunc. This test currently FAILS because the safety net is not yet implemented. Refs: docker#2268 Assisted-By: docker-agent
When the user types /exit, bubbletea's cursedRenderer can deadlock: its ticker-driven flush goroutine holds a mutex while blocked writing to stdout, and the event loop's final render() call after tea.Quit blocks on the same mutex. p.Run() never returns and the process hangs. Add a safety-net goroutine in cleanupAll() that calls os.Exit(0) after 5 seconds, guaranteeing the process terminates even when bubbletea's renderer is deadlocked. Fixes docker#2268 Assisted-By: docker-agent
dgageot
approved these changes
Mar 27, 2026
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Fixes #2268
Problem
After typing
/exit, the docker-agent process hangs indefinitely. The rootcause is a mutex deadlock inside bubbletea v2's
cursedRenderer: therenderer's ticker-driven
flushgoroutine holds a mutex while blocked on awritesyscall to stdout (terminal buffer full), and the event loop's finalrender()call aftertea.Quitblocks trying to acquire the same mutex.See #2268 for full diagnostic including goroutine dumps and sequence diagram.
Solution
Add a safety-net goroutine in
cleanupAll()that callsos.Exit(0)after a5-second timeout. This guarantees the process terminates even when bubbletea's
renderer is deadlocked.
The timeout and exit function are exposed as package-level variables
(
shutdownTimeout,exitFunc) so tests can override them.Tests
TestExitDeadlock_BlockedStdout— proves the bubbletea deadlock exists(p.Run never returns when stdout blocks during the final render)
TestCleanupAll_SpawnsSafetyNet— verifiescleanupAllspawns thesafety-net goroutine that calls
exitFuncafter the timeoutTestExitSafetyNet_BlockedStdout— end-to-end: blocked stdout + safetynet fires
TestExitSafetyNet_GracefulShutdown— verifies the safety net does NOTfire during normal shutdown (no blocked stdout)