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H A D | bug.h | ccd0d44f Fri Mar 25 15:21:06 CDT 2011 Steven Rostedt <srostedt@redhat.com> WARN_ON_SMP(): Add comment to explain ({0;})
The define to use ({0;}) for the !CONFIG_SMP case of WARN_ON_SMP() can be confusing. As the WARN_ON_SMP() needs to be a nop when CONFIG_SMP is not set, including all its parameters must not be evaluated, and that it must work as both a stand alone statement and inside an if condition, we define it to a funky ({0;}).
A simple "0" will not work as it causes gcc to give the warning that the statement has no effect.
As this strange definition has raised a few eyebrows from some major kernel developers, it is wise to document why we create such a work of art.
Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> ccd0d44f Fri Mar 25 15:21:06 CDT 2011 Steven Rostedt <srostedt@redhat.com> WARN_ON_SMP(): Add comment to explain ({0;}) The define to use ({0;}) for the !CONFIG_SMP case of WARN_ON_SMP() can be confusing. As the WARN_ON_SMP() needs to be a nop when CONFIG_SMP is not set, including all its parameters must not be evaluated, and that it must work as both a stand alone statement and inside an if condition, we define it to a funky ({0;}). A simple "0" will not work as it causes gcc to give the warning that the statement has no effect. As this strange definition has raised a few eyebrows from some major kernel developers, it is wise to document why we create such a work of art. Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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