> >> >
> >> > + 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 <[email protected]>
--- 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 è uno flexible tool per seguire di logfiles e effettuazione
di commissioni. Feltrare, provedere da colore, merge, 'diff-view',
etc. http://www.vanheusden.com/multitail/
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