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Re: why "in_sighandler"?
From: |
YAMAMOTO Mitsuharu |
Subject: |
Re: why "in_sighandler"? |
Date: |
Tue, 22 Aug 2006 17:34:51 +0900 |
User-agent: |
Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.6 (Marutamachi) APEL/10.6 Emacs/22.0.50 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI) |
>>>>> On Tue, 22 Aug 2006 10:23:40 +0200, Jan Djärv <address@hidden> said:
>>> How can it be otherwise? If you only have one program counter,
>>> that program counter must be changed to the signal handler no
>>> matter how many threads you have, i.e. any previous execution
>>> (regardless of thread) is interrupted.
>>
>> Not-running threads have already been *interrupted* by context
>> switching. Are they interrupted by a signal again?
> What exactly do you mean by interrupted? In the sense that they
> don't get to execute, yes they are interrupted.
I should have used "..." instead of *...*. I tried to follow your
definition of "interrupt".
> When a signal handler is running, no threads can run (on a single
> CPU machine), hence they are all interrupted.
The signalled-thread is/becomes running just before the signal handler
is executed. The thread is not "interrupt"ed by context switching,
but by a signal.
>> I don't understand why non-signalled threads are relevant as long
>> as a signal handler only executes thread-safe functions. The
>> problem of async-signal-unsafe function is that a thread that took
>> a lock in the normal context may try to take the same lock in a
>> signal handler context. The thread cannot go back to the normal
>> context where the lock will be released afterwards, but just waits
>> for the lock in the signal handler. As a result, the thread gets
>> stuck. That's irrelevant to the other threads.
> That can't be it. The mutex is recursive, so a thread is able to
> take it multiple times.
Recursive mutex is implemented using a simpler lock mechanism. That's
why I used the term "lock" instead of "mutex".
YAMAMOTO Mitsuharu
address@hidden
- Re: why "in_sighandler"?, (continued)
- Re: why "in_sighandler"?, YAMAMOTO Mitsuharu, 2006/08/21
- Re: why "in_sighandler"?, Jan Djärv, 2006/08/21
- Re: why "in_sighandler"?, YAMAMOTO Mitsuharu, 2006/08/21
- Re: why "in_sighandler"?, Jan Djärv, 2006/08/21
- Re: why "in_sighandler"?, YAMAMOTO Mitsuharu, 2006/08/21
- Re: why "in_sighandler"?, Jan Djärv, 2006/08/21
- Re: why "in_sighandler"?, YAMAMOTO Mitsuharu, 2006/08/21
- Re: why "in_sighandler"?, Jan Djärv, 2006/08/22
- Re: why "in_sighandler"?, YAMAMOTO Mitsuharu, 2006/08/22
- Re: why "in_sighandler"?, Jan Djärv, 2006/08/22
- Re: why "in_sighandler"?,
YAMAMOTO Mitsuharu <=
- Re: why "in_sighandler"?, Jan Djärv, 2006/08/22
- Re: why "in_sighandler"?, Andreas Schwab, 2006/08/22
Re: why "in_sighandler"?, Richard Stallman, 2006/08/21