From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 20 May 2007 22:55:00 +0200 From: Folkert van Heusden Subject: Re: signals logged / [RFC] log out-of-virtual-memory events Message-ID: <20070520205500.GJ22452@vanheusden.com> References: <464C9D82.60105@redhat.com> <200705181347.14256.ak@suse.de> <20070520001418.GJ14578@vanheusden.com> <464FC6AA.2060805@cosmosbay.com> <20070520112111.GN14578@vanheusden.com> <20070520090809.4f42d71d@freepuppy> <20070520161159.GD22452@vanheusden.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Jan Engelhardt Cc: Stephen Hemminger , Eric Dumazet , Andi Kleen , Rik van Riel , righiandr@users.sourceforge.net, LKML , linux-mm@kvack.org List-ID: > >> > > >> > + if (unlikely(sig == SIGQUIT || sig == SIGILL || sig == SIGTRAP || > >> > + sig == SIGABRT || sig == SIGBUS || sig == SIGFPE || > >> > + sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ || > >> > + sig == SIGSYS || sig == SIGSTKFLT)) > >> > + { > >> > + printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n", > >> > + sig, t->pid, t->uid, t->gid, t->comm); > >> > + } > >> > + > >> > /* > >> > * fast-pathed signals for kernel-internal things like SIGSTOP > >> > * or SIGKILL. > >> Would turning that into a switch() generate better code. > Yes, this time. > > >Doubt it: in the worst case you still nee to check for each possibility. > >Furthermore a.f.a.i.k. with switch you cannot do 'unlinkely()'. > > With if(), it generates a ton of "CMP, JE" instructions. > With switch(), I would assume gcc transforms it into using > a jump table (aka "JMP [table+sig]") > I tried it: with switch(), gcc transforms this into a > bitmap comparison ("MOV eax, 1; SHL eax, sig; TEST eax, 0x830109f8"), > which seems even cheaper than a jump table. Ok, here's the new patch against 2.6.21.1: Signed-off by Folkert van Heusden --- kernel/signal.c.org 2007-05-20 22:47:13.000000000 +0200 +++ kernel/signal.c 2007-05-20 22:54:17.000000000 +0200 @@ -739,6 +739,25 @@ struct sigqueue * q = NULL; int ret = 0; + /* emit some logging for nasty signals + * especially SIGSEGV and friends aught to be looked at when happening + */ + switch(sig) { + case SIGQUIT: + case SIGILL: + case SIGTRAP: + case SIGABRT: + case SIGBUS: + case SIGFPE: + case SIGSEGV: + case SIGXCPU: + case SIGXFSZ: + case SIGSYS: + case SIGSTKFLT: + printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n", + sig, t -> pid, t -> uid, t -> gid, t -> comm); + } + /* * fast-pathed signals for kernel-internal things like SIGSTOP * or SIGKILL. Folkert van Heusden -- MultiTail e uno flexible tool per seguire di logfiles e effettuazione di commissioni. Feltrare, provedere da colore, merge, 'diff-view', etc. http://www.vanheusden.com/multitail/ ---------------------------------------------------------------------- Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org