On Tuesday 16 September 2008 23:57, Michael Trimarchi wrote: > Hi, > > > > ----- Messaggio originale ----- > > > Da: Nick Piggin <nickpiggin@xxxxxxxxxxxx> > > A: Michael Trimarchi <trimarchimichael@xxxxxxxx> > > Cc: Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>; > > akpm@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > linux-fsdevel@xxxxxxxxxxxxxxx Inviato: Martedì 16 settembre 2008, > > 14:54:21 > > Oggetto: Re: [PATCH] VFS: make file->f_pos access atomic on 32bit arch > > > > On Tuesday 16 September 2008 21:11, Michael Trimarchi wrote: > > > Hi, > > > > > > > + if (offset != file_pos_read(file)) > > > > + file_pos_write(file, offset); > > > > retval = offset; > > > > } > > > > > > Is not more efficient here a compare xchg operation? > > > > The compiler should do it if it was. > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" > > in the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > i was thinking about introducing a file_pos_update() not implemented using > file_pos_read()/file_pos_write() and taking the seq_lock or > disabling preemption only one time AFAIK, the only way to do an atomic 64 bit store on 32-bit x86 is "cmpxchg8b" (with lock prefix on SMP). That would be far slower I'm sure. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
