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Title: synchronous signals blocked in pthreads
Type: Stage:
Components: Interpreter Core Versions: Python 2.3
Status: closed Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: dmaurer, gvanrossum, langmead, mwh, tim.peters
Priority: high Keywords: patch

Created on 2004-05-06 17:07 by langmead, last changed 2022-04-11 14:56 by admin. This issue is now closed.

File name Uploaded Description Edit
syncsigstothreads.diff langmead, 2004-05-06 17:07 unblocks syncronous signals
Messages (7)
msg45955 - (view) Author: Andrew Langmead (langmead) Date: 2004-05-06 17:07
In a pthreads environment, signals sent asynchronously 
from things like kill() or the terminal driver are sent to the 
process and can be handled by any thread. Signals that are 
sent synchronously from the instruction stream (signals like 
SIGSEGV, SIGFPE, or  SIGILL) are only delivered to the 
thread that executed the instruction.

The current Python threads, when implemented via  
pthreads, blocks these synchronous signals and so thread 
that generates one can hang the entire process.

The attached patch will remove some signals the list of 
signals to be blocked. The list of signals to be removed 
correspond to signals that can be generated synchronously.

msg45956 - (view) Author: Tim Peters (tim.peters) * (Python committer) Date: 2004-05-06 18:11
Logged In: YES 

Boosted the priority in the hopes this will get looked at before 
2.3.4.  Unfortunately, I'm not in a position to test a pthreads 

I'll note that the good comments about *why* this change is 
being entertained would be far more useful in the code than in 
the patch comment here.
msg45957 - (view) Author: Guido van Rossum (gvanrossum) * (Python committer) Date: 2004-05-11 13:47
Logged In: YES 

As Tim mentioned, this is a possible stopgap fix for bug 949332.

While many objections have been raised, I still think this
is a safer approach than some of the more advanced suggestions.

(Too bad it doesn't solve my own, related problem, which is
that SIGTERM is ignored by default in a process started from
a Python thread.)
msg45958 - (view) Author: Dieter Maurer (dmaurer) Date: 2004-05-26 10:46
Logged In: YES 

This patch addresses a serious problem in Zope2 (and
probably other multi-threaded) production environments with
LinuxThreads. A crash of one thread brings other threads in
an unsane state which they leave only on "kill -9". This
lets Guido's "zdeamon" automatic restart logic fail. Even
manual restarts are a bit difficult as each individual
thread must be sent a "kill -9".

Applying the patch lets at least the process die properly. I
am not yet sure whether the return code is appropriate for
"zdeamon" to restart the process. I will check that soon and
report back.
msg45959 - (view) Author: Dieter Maurer (dmaurer) Date: 2004-05-26 12:00
Logged In: YES 

I verified that the return code is appropriate.
msg45960 - (view) Author: Andrew Langmead (langmead) Date: 2004-05-26 16:38
Logged In: YES 

The changes in <
?func=detail&aid=960406&group_id=5470&atid=305470> are 
probably more appropriate than this patch.
msg45961 - (view) Author: Michael Hudson (mwh) (Python committer) Date: 2004-05-28 08:50
Logged In: YES 

Closing in favour of 960406.
Date User Action Args
2022-04-11 14:56:04adminsetgithub: 40227
2004-05-06 17:07:25langmeadcreate