Tinyconfig build failures in v6.6.y and v6.12.y due to "srcu: Use irq_work to start GP in tiny SRCU"

Tinyconfig build failures in v6.6.y and v6.12.y due to "srcu: Use irq_work to start GP in tiny SRCU"

[Guenter Roeck]

Hi,

I see lots of tinyconfig build failures in v6.6.y and v6.12.y.
Current release candidates are also affected.

Example from v6.12.y:

Building csky:tinyconfig ... failed
--------------
Error log:
/opt/kernel/gcc-14.4.0-2.47-nolibc/csky-linux/bin/csky-linux-ld: kernel/rcu/srcutiny.o: in function `cleanup_srcu_struct':
srcutiny.c:(.text+0x2a): undefined reference to `irq_work_sync'
/opt/kernel/gcc-14.4.0-2.47-nolibc/csky-linux/bin/csky-linux-ld: kernel/rcu/srcutiny.o: in function `srcu_gp_start_if_needed':
srcutiny.c:(.text+0x60): undefined reference to `irq_work_queue'
/opt/kernel/gcc-14.4.0-2.47-nolibc/csky-linux/bin/csky-linux-ld: kernel/rcu/srcutiny.o: in function `start_poll_synchronize_srcu':
srcutiny.c:(.text+0xb8): undefined reference to `irq_work_sync'
/opt/kernel/gcc-14.4.0-2.47-nolibc/csky-linux/bin/csky-linux-ld: srcutiny.c:(.text+0xc8): undefined reference to `irq_work_queue'
make[3]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1

Bisect points to commit 58dd6e92725f ("srcu: Use irq_work to start GP in tiny SRCU")
in v6.12.y. Reverting this commit fixes the problem.

Problem is that IRQ_WORK is not enabled with tinyconfig in v6.6.y
and v6.12.y. In later kernels it is enabled due to the unrelated
commit af92793e52c3a ("slab: Introduce kmalloc_nolock() and
kfree_nolock().") which adds "select IRQ_WORK" to "config SLUB".

Adding "select IRQ_WORK" to "config TINY_SRCU" also fixes the build
problem, but I don't know if that is an acceptable / desirable solution.
If so, it should probably be added to the mainline kernel since the code
only builds there accidentally. I'll leave that up to RCU and stable
release maintainers to decide.

Bisect log is attached for reference.

Thanks,
Guenter

---
# bad: [9fb48106e91d81010e61a7fa0b09aa6081ff1a2f] Linux 6.12.114-rc2
# good: [7fdb7c1824a1f9979d648d7ae28ac446bcee9c6e] Linux 6.12.113
git bisect start 'HEAD' 'v6.12.113'
# bad: [fbf5bbbfe00526982e83b55a3aebed9096503646] netfs: Clean up some whitespace in trace header
git bisect bad fbf5bbbfe00526982e83b55a3aebed9096503646
# good: [27d90b6cd0a460f1f3a9678ef45312b803a0ccb5] mpls: Add mpls_route_input().
git bisect good 27d90b6cd0a460f1f3a9678ef45312b803a0ccb5
# bad: [86baeb912a990effd375019875fcf39fdabf56b5] net: phonet: do not BUG_ON() in pn_socket_autobind() on failed bind
git bisect bad 86baeb912a990effd375019875fcf39fdabf56b5
# bad: [78543c82d93b6bb10c7d6527138b7c99ecb2c2c3] net: stmmac: fix oops when split header is enabled
git bisect bad 78543c82d93b6bb10c7d6527138b7c99ecb2c2c3
# bad: [5c95382ad671b086e361c5bb94678754512bfc59] media: chips-media: wave5: Fix Null reference while testing fluster
git bisect bad 5c95382ad671b086e361c5bb94678754512bfc59
# good: [4e2cee549890df21dc0d06f9bbc2df98e8dbc60b] irqwork: Move data struct to a types header
git bisect good 4e2cee549890df21dc0d06f9bbc2df98e8dbc60b
# bad: [568deb5ecc2624ea189ecda36162962725bd6827] wifi: iwlwifi: fix 22000 series SMEM parsing
git bisect bad 568deb5ecc2624ea189ecda36162962725bd6827
# bad: [d0b39dc7649b68bdeaa17c71c76d58eab59a35c7] btrfs: fix zero size inode with non-zero size after log replay
git bisect bad d0b39dc7649b68bdeaa17c71c76d58eab59a35c7
# bad: [7dabc9bec015ccad262d8cc37e8c00328f555691] btrfs: tree-log: don't use token set/get accessors in fill_inode_item(
)
git bisect bad 7dabc9bec015ccad262d8cc37e8c00328f555691
# bad: [58dd6e92725f9afc375ccb11d3ef04fab0a4b4af] srcu: Use irq_work to start GP in tiny SRCU
git bisect bad 58dd6e92725f9afc375ccb11d3ef04fab0a4b4af
# first bad commit: [58dd6e92725f9afc375ccb11d3ef04fab0a4b4af] srcu: Use irq_work to start GP in tiny SRCU

Re: Tinyconfig build failures in v6.6.y and v6.12.y due to "srcu: Use irq_work to start GP in tiny SRCU"

[Sasha Levin]

> Bisect points to commit 58dd6e92725f ("srcu: Use irq_work to start GP in tiny SRCU")
> in v6.12.y. Reverting this commit fixes the problem.

Queued the revert for 6.12 and 6.6, thanks.

> Adding "select IRQ_WORK" to "config TINY_SRCU" also fixes the build
> problem, but I don't know if that is an acceptable / desirable solution.
> If so, it should probably be added to the mainline kernel since the code
> only builds there accidentally.

That one is for Joel and the RCU maintainers to take up in mainline.

-- 
Thanks,
Sasha

Re: Tinyconfig build failures in v6.6.y and v6.12.y due to "srcu: Use irq_work to start GP in tiny SRCU"

[Joel Fernandes]

On Mon, Oct 26, 2026 at 06:55:52PM -0400, Sasha Levin wrote:
> > Bisect points to commit 58dd6e92725f ("srcu: Use irq_work to start GP in tiny SRCU")
> > in v6.12.y. Reverting this commit fixes the problem.
> 
> Queued the revert for 6.12 and 6.6, thanks.
> 
> > Adding "select IRQ_WORK" to "config TINY_SRCU" also fixes the build
> > problem, but I don't know if that is an acceptable / desirable solution.
> > If so, it should probably be added to the mainline kernel since the code
> > only builds there accidentally.
> 
> That one is for Joel and the RCU maintainers to take up in mainline.

Thank you for the suggestion, I will add it for 7.5.

thanks,

Joel Fernandes