Sorry, I misread the OP as artists calling out themselves.:smack:
in “Back In My Arms Again”, Diana Ross namechecks both Florence Ballard and Mary Wilson of the original Supremes group:
[ol]
[/ol]The Paula Abdul & MC Skat Cat single of Opposites Attract in the intro: “I’m M.C. Kat on the rap so mic it/Here’s a little story and you’re sure to like it/Swift and sly and I’m playing it cool/With my home girl, Paula Abdul”
Keeping with Paula Abdul, the album version of Vibeology has a “Go Paula Go Paula!” chant in it by the back up singers.
A little less part of the song structure, the outro of the album version of “The Way That You Love Me” has a Go Paula! sung by a backup singer in it.
And there’s probably more I’m forgetting.
Yes, I listened to a lot of Paula Abdul growing up. What of it? 
OK, can OP clarify? I’m getting the sense that half these answers aren’t what the OP is looking for. Or am I misunderstanding the question:
I’m taking that to mean that the main performer of the song is being named checked in their own song by somebody else who is not them. Like in the Shakira song: she sings “Hips Don’t Lie.” In the song, her name is called out by a background vocalist. In the Chakha Khan song, the main song is sung by Chakha Khan, but she is referenced in the intro (and elsewhere) by a secondary, male singer. The Carlos Santana one is a bit more ambiguous, as Carlos Santana doesn’t really sing main vocals, so, in this case, it is the lead vocalist calling him out, but he’s the “main artist” in that the band is Santana, and he is the artist that defines the band.
Many of the examples here seem to be the run-of-the-mill namechecks is OP is specifically not looking for: “There are also many, many examples of singers mentioning other singers. I’m not talking about those.”
Am I the one confused?
Pulykamell, you have it exactly right, and probably explained it better than I did.
So, for example, “Play it, Steve!” From Soul Man does not fit. But if Steve had yelled out “Sing it, Sam and Dave!” It would.
I assume you’ll find a number of examples in the hip-hop universe. The most obvious one would be “Who Am I (What’s My Name)” by Snoop Dogg, where the entire hook is background singers singing “Snoop Doggy Dog.” Does that count for your purposes?
Billy Joel in Piano Man
Clap for the Wolfman by the Guess Who. Except the Wolfman is the guest artist and the band is singing about him.
Billy (not someone else) is singing his own name.
From John Lennon in Glass Onion
I told you about the walrus and me, man
You know we’re as close as can be, man
Well here’s another clue for you all
The walrus was Paul.
(McCartney)
Eminem name checks Kid Rock and Twisted Brown Trucker in Kid Rock’s “Fuck Off”
Goldfinger - “Carlita” includes guest vocals and saxophone by Angelo Moore of Fishbone and just before the breakdown he calls out “Play it Goldfinger!”
This may not satisfy a strict OP, but it’s satisfying none the less…
Jeb Loy Nichols name-checks so many country/reggae/soul/dub artists in so many songs that back in 1990, a couple of us vowed to listen to them all. One verse of “This Summer” goes:
Spin the disk, Mr. DJ, spin the disk, Mr. DJ…
We got Tony Joe White, we got Merle Haggard,
Culture and The Mighty Heaters.
We got Bobby Womack and Curtis Mayfield…
…this summer.
The Girl is Mine by Michael Jackson, featuring Paul McCartney has this exchange:
“Michael, we’re not going to fight about this, okay
Paul, I think I told you, I’m a lover not a fighter”
The earworm-y folk-pop song “Home” by Edward Sharpe and the Magnetic Zeros has a spoken dialogue bridge that begins with both vocalists addressing each other by name (“Jade?” “Alexander?”). The whole bridge is removed from the common radio version, though.
Simon and Garfunkel’s A Simple Desultory Philippic has these lines:
The Beatles’ Honey Don’t: “Ah, rock on, George, for Ringo one time”.
Maroon 5s- “Moves like Jagger”
Aerosmith covered "Come Together " the line “Ono sideboard” (I know, yes she’s an Artist)
Hayes Carll mentions Dylan in “Another like You”
And he also has a song where he says “I’m like James Brown, only white and taller”
The song is “Stomp and Holler”
Oops. I may have misunderstood the OP.
Ignore my post above.
This doesn’t really match the OP’s requirements since it’s about the songwriter not the lead singer, but in the Captain and Tennille version of Love Will Keep Us Together on the fadeout they sing “Sedaka is back”.
I think this counts…
The remake of Lady Marmalade from Moulin Rouge is sung by Christina Aguilera, Lil’ Kim, Mya and Pink.
At the end of the song the producer, Missy Elliot, calls out the names of the four singers.