Date: Sun, 24 Feb 2002 10:55:08 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Terry Lambert <tlambert2@mindspring.com>, Alfred Perlstein <alfred@FreeBSD.ORG>, Bosko Milekic <bmilekic@unixdaemons.com>, Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp>, <current@FreeBSD.ORG>, John Baldwin <jhb@FreeBSD.ORG> Subject: Re: malloc_bucket() idea (was Re: How to fix malloc.) Message-ID: <20020224105118.L30818-100000@gamplex.bde.org> In-Reply-To: <200202232312.g1NNCaH54765@apollo.backplane.com>
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On Sat, 23 Feb 2002, Matthew Dillon wrote: > critical_enter() isn't much better then a mutex. It can > be optimized to get rid of the inline cli & sti however. Actually, it > can be optimized trivially for i386, all we have to do is check the > critical nesting count from the interrupt code and set the > interrupts-disabled bit in the returned (supervisor mode) frame. > > critical_enter() and critical_exit() would then be nearly perfect. My version of it does less than this. I only use it to help implement spinlocks. Index: kern_switch.c =================================================================== RCS file: /home/ncvs/src/sys/kern/kern_switch.c,v retrieving revision 1.20 diff -u -2 -r1.20 kern_switch.c --- kern_switch.c 11 Feb 2002 20:37:51 -0000 1.20 +++ kern_switch.c 13 Feb 2002 05:34:20 -0000 @@ -70,14 +70,21 @@ } -/* Critical sections that prevent preemption. */ +/*- + * Critical section handling. + * XXX doesn't belong here. + * + * Entering a critical section only blocks non-fast interrupts. + * critical_enter() is similar to splhigh() in a 2-level spl setup under + * old versions of FreeBSD. + * + * Exiting from all critical sections unblocks non-fast interrupts and runs + * the handlers of any that were blocked. critical_exit() is similar to + * spl(old_level) in a 2-level spl setup under old versions of FreeBSD. + */ void critical_enter(void) { - struct thread *td; - td = curthread; - if (td->td_critnest == 0) - td->td_savecrit = cpu_critical_enter(); - td->td_critnest++; + curthread->td_critnest++; } @@ -85,12 +92,7 @@ critical_exit(void) { - struct thread *td; - td = curthread; - if (td->td_critnest == 1) { - td->td_critnest = 0; - cpu_critical_exit(td->td_savecrit); - } else - td->td_critnest--; + if (--curthread->td_critnest == 0 && (ipending | spending) != 0) + unpend(); } Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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