Bug #42454 Check return value of pthread_mutex_lock
Submitted: 29 Jan 15:06 Modified: 30 Jan 12:03
Reporter: Jørgen Austvik
Status: Verified
Category:Server: General Severity:S4 (Feature request)
Version:5.0-bzr, 5.1-bzr, 6.0-bzr OS:Any
Assigned to: Target Version:
Triage: Needs Triage: D5 (Feature request)

[29 Jan 15:06] Jørgen Austvik 
Description:
Lots of places in the MySQL source code, we call pthread_mutex_lock(3C) without checking
the return value for an error condition. Examples: 

my_open.c:
      pthread_mutex_lock(&THR_LOCK_open);

my_pthread.h:
#define thread_safe_increment(V,L) \
        (pthread_mutex_lock((L)), (V)++, pthread_mutex_unlock((L)))
#define thread_safe_decrement(V,L) \
        (pthread_mutex_lock((L)), (V)--, pthread_mutex_unlock((L)))

pthread_mutex_lock() can fail with at least five different errors, if one of these
happens, the call returns and the code will continue to run (thinking it has the mutex)
even though the mutex is not locked.

How to repeat:
Use the source, Luke.

Suggested fix:
Check return value of pthread_mutex_lock(3C) with friends.
[30 Jan 12:03] Valeriy Kravchuk 
Verified by code review.