[PATCH] SCSI: buslogic: reduce stack usage

[PATCH] SCSI: buslogic: reduce stack usage

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Some randconfig builds run into excessive stack usage with gcc-14 or
higher, which use __attribute__((cold)) where earlier versions did
not do that:

drivers/scsi/BusLogic.c: In function 'blogic_init':
drivers/scsi/BusLogic.c:2398:1: error: the frame size of 1680 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]

The problem is that a lot of code gets inlined into blogic_init()
here. Two functions stick out, but they are a bit different:

 - blogic_init_probeinfo_list() actually uses a few hundred bytes of
   kernel stack, which is a problem in combination with other functions
   that also do. Marking this one as noinline means that the stack slots
   get get reused between function calls

 - blogic_reportconfig() has a few large variables, but whenever it is
   not inlined into its caller, the compiler is actually smart enough
   to reuse stack slots for these automatically, so marking it as
   noinline saves most of the stack space by itself.

The combination of both of these should avoid the problem entirely.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/scsi/BusLogic.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/BusLogic.c b/drivers/scsi/BusLogic.c
index 865fcbac8fa1..49929d0339fa 100644
--- a/drivers/scsi/BusLogic.c
+++ b/drivers/scsi/BusLogic.c
@@ -920,7 +920,8 @@ static int __init blogic_init_fp_probeinfo(struct blogic_adapter *adapter)
   a particular probe order.
 */
 
-static void __init blogic_init_probeinfo_list(struct blogic_adapter *adapter)
+static noinline_for_stack void __init
+blogic_init_probeinfo_list(struct blogic_adapter *adapter)
 {
 	/*
 	   If a PCI BIOS is present, interrogate it for MultiMaster and
@@ -1690,7 +1691,8 @@ static bool __init blogic_rdconfig(struct blogic_adapter *adapter)
   blogic_reportconfig reports the configuration of Host Adapter.
 */
 
-static bool __init blogic_reportconfig(struct blogic_adapter *adapter)
+static noinline_for_stack bool __init
+blogic_reportconfig(struct blogic_adapter *adapter)
 {
 	unsigned short alltgt_mask = (1 << adapter->maxdev) - 1;
 	unsigned short sync_ok, fast_ok;
-- 
2.39.5

Re: [PATCH] SCSI: buslogic: reduce stack usage

[Martin K. Petersen]

Arnd,

> Some randconfig builds run into excessive stack usage with gcc-14 or
> higher, which use __attribute__((cold)) where earlier versions did not
> do that:

Applied to 6.20/scsi-staging, thanks!

-- 
Martin K. Petersen

Re: [PATCH] SCSI: buslogic: reduce stack usage

[Maciej W. Rozycki]

On Tue, 3 Feb 2026, Arnd Bergmann wrote:

> Some randconfig builds run into excessive stack usage with gcc-14 or
> higher, which use __attribute__((cold)) where earlier versions did
> not do that:
> 
> drivers/scsi/BusLogic.c: In function 'blogic_init':
> drivers/scsi/BusLogic.c:2398:1: error: the frame size of 1680 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]

 Probably obviously correct, but still:

Tested-by: Maciej W. Rozycki <macro@orcam.me.uk>

-- with GCC 15 and a BT-958 MultiMaster host adapter, and the rootfs as 
well as most other filesystems on devices downstream.  This is with 
slightly older 6.19.0-rc1 from the pci repo, which I've had handy from 
other verification and should not matter for the scope of this testing.

  Maciej

Re: [PATCH] SCSI: buslogic: reduce stack usage

[Martin K. Petersen]

On Tue, 03 Feb 2026 17:33:15 +0100, Arnd Bergmann wrote:

> Some randconfig builds run into excessive stack usage with gcc-14 or
> higher, which use __attribute__((cold)) where earlier versions did
> not do that:
> 
> drivers/scsi/BusLogic.c: In function 'blogic_init':
> drivers/scsi/BusLogic.c:2398:1: error: the frame size of 1680 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
> 
> [...]

Applied to 6.20/scsi-queue, thanks!

[1/1] SCSI: buslogic: reduce stack usage
      https://git.kernel.org/mkp/scsi/c/e17f0d4cc006

-- 
Martin K. Petersen