On Dec 30, 2014, "Carlos O'Donell" <carlos@xxxxxxxxxx> wrote: > Note that reetrant functions need not be AS-safe nor MT-safe. How? I suppose it might depend on the definition of reentrant, but if you can reenter it in multiple threads, and you can reenter it within a thread in which it is active (e.g., in a signal handler that may have interrupted its own execution), then it definitely is reentrant. Conversely, if it is reentrant, then you can safely reenter it in multiple threads (MT-Safe) and within signal handlers (AS-Safe), no? What definition of reentrant could make a function be reentrant without being both MT- and AS-Safe, or be both MT- and AS-Safe without being reentrant? I suppose there might be scenarios in which a function doesn't qualify for AS-Safe because it doesn't support async recursion, but it could still be reentered by means of (indirect?) recursion safely. However, I can't see how this could be the case without the function being at least MT-Safe. It looks like any window that could bring trouble for async signals would also do so for other threads. Unless... Recursive locks? Those would avoid trouble for other threads (making the function MT-Safe), but not for async signals (so AS-Unsafe), and sync recursion could enable reentrancy while avoid pitfalls that async signals would bring about and that recursive locks wouldn't aovid. Is this the case you had in mind? Is it the only one in which a function can be Reentrant, MT-Safe and AS-Unsafe? Can you think of any that is AS-Safe, MT-Unsafe and Reentrant? Can you think of any that is AS-Unsafe, MT-Unsafe and Reentrant? Can you think of any that is non-Reentrant but that is MT-Safe or AS-Safe? -- Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/ You must be the change you wish to see in the world. -- Gandhi Be Free! -- http://FSFLA.org/ FSF Latin America board member Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
