Bug #16670 Thread alarms cause havoc on cooperative multithreading systems (SCO..)

• Submitted: 20 Jan 2006 13:34
• Modified: 21 Jan 2006 12:38
• Reporter: Domas Mituzas
• Status: Unsupported
• Category: MySQL Server
• Severity: S2 (Serious)
• Version: 5.0.18
• OS: Other (SCO OpenServer 5.0.7)
• CPU Architecture: Any

[20 Jan 2006 13:34] Domas Mituzas

Description:
In cooperative multithreading environments ALRM signal interrupts any syscalls hapenning for whole instance, therefore interrupting proper workflow of clients and server. 

e.g. accept() call for a unix domain socket would immediately deliver EINTR to connect()'ing client. 

Excessive signaling possibly appeared after 5.0.16.

How to repeat:
kill -ALRM server during any syscall, when alarm handler is installed, observe consequences.

Suggested fix:
Replace alarm signals with signal-less notification methods, async calls, spinloops, etc. 
Allow more efficient reconnect on failed connections in libmysqlclient and mysql cli.

[20 Jan 2006 13:58] Domas Mituzas

gdb traps many SIGALRMs.