| Message ID | 20190617131733.2429469-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | dmaengine: dw-edma: fix unnecessary stack usage | expand |
Hi, On Mon, Jun 17, 2019 at 14:16:45, Arnd Bergmann <arnd@arndb.de> wrote: > Putting large constant data on the stack causes unnecessary overhead > and stack usage: > > drivers/dma/dw-edma/dw-edma-v0-debugfs.c:285:6: error: stack frame size of 1376 bytes in function 'dw_edma_v0_debugfs_on' [-Werror,-Wframe-larger-than=] I had that warning at the beginning of the development, that's why I divided the debugfs entries into several subfunctions. Perhaps my configuration has configured a bigger stack frame size than your configuration. > > Mark the variable 'static const' in order for the compiler to move it > into the .rodata section where it does no such harm. Ok, sounds good. Thanks. > > Fixes: 305aebeff879 ("dmaengine: Add Synopsys eDMA IP version 0 debugfs support") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/dma/dw-edma/dw-edma-v0-debugfs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c > index affa1ccaf7a0..42739508c0d8 100644 > --- a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c > +++ b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c > @@ -48,7 +48,7 @@ static struct { > } lim[2][EDMA_V0_MAX_NR_CH]; > > struct debugfs_entries { > - char name[24]; > + const char *name; > dma_addr_t *reg; > }; > > -- > 2.20.0
On Fri, Jun 21, 2019 at 10:21 AM Gustavo Pimentel <Gustavo.Pimentel@synopsys.com> wrote: > On Mon, Jun 17, 2019 at 14:16:45, Arnd Bergmann <arnd@arndb.de> wrote: > > > Putting large constant data on the stack causes unnecessary overhead > > and stack usage: > > > > drivers/dma/dw-edma/dw-edma-v0-debugfs.c:285:6: error: stack frame size of 1376 bytes in function 'dw_edma_v0_debugfs_on' [-Werror,-Wframe-larger-than=] > > I had that warning at the beginning of the development, that's why I > divided the debugfs entries into several subfunctions. Perhaps my > configuration has configured a bigger stack frame size than your > configuration. I suspect the problem is CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE, which is a farily new configuration option that has the unintended side-effect of sometimes preventing the compiler combining local variables from functions inlined into the caller. Adding 'noinline_for_stack' to the sub-functions would have also prevented this, but I think just not having the strings on the stack is better anyway. Arnd
diff --git a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c index affa1ccaf7a0..42739508c0d8 100644 --- a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c +++ b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c @@ -48,7 +48,7 @@ static struct { } lim[2][EDMA_V0_MAX_NR_CH]; struct debugfs_entries { - char name[24]; + const char *name; dma_addr_t *reg; };
Putting large constant data on the stack causes unnecessary overhead and stack usage: drivers/dma/dw-edma/dw-edma-v0-debugfs.c:285:6: error: stack frame size of 1376 bytes in function 'dw_edma_v0_debugfs_on' [-Werror,-Wframe-larger-than=] Mark the variable 'static const' in order for the compiler to move it into the .rodata section where it does no such harm. Fixes: 305aebeff879 ("dmaengine: Add Synopsys eDMA IP version 0 debugfs support") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/dma/dw-edma/dw-edma-v0-debugfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)