Date: Thu, 21 Jan 1999 10:46:57 +1100 From: Bruce Evans <bde@zeta.org.au> To: green@unixhelp.org, mike@smith.net.au Cc: current@FreeBSD.ORG Subject: Re: Truth to M_WAITOK? Message-ID: <199901202346.KAA13074@godzilla.zeta.org.au>
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>It looks like M_WAITOK will either return non-NULL or panic; it >shouldn't be capable of returning NULL. Ideally, it shouldn't panic >either (why is it only that M_WAITOK can panic, and M_NOWAIT can't?). Because failures for M_NOWAIT are normal (all pages may be in use, and the caller is not prepared for pages top be freed by swapping). Therefore, callers that set M_NOWAIT must be prepared for failure. OTOH, failures for M_WAITOK are abnormal, and at least for map == kmem_map (as it is for calls to kmem_malloc() from malloc()), the correct handling for failure is to panic since a full map is unlikely to become unfull and neither the caller or kmem_malloc() can know what to do to unfill it. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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