From 2ce802f62ba32a7d95748ac92bf351f76affb6ff Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 20 Jan 2011 12:06:35 +0100 Subject: lockdep: Move early boot local IRQ enable/disable status to init/main.c During early boot, local IRQ is disabled until IRQ subsystem is properly initialized. During this time, no one should enable local IRQ and some operations which usually are not allowed with IRQ disabled, e.g. operations which might sleep or require communications with other processors, are allowed. lockdep tracked this with early_boot_irqs_off/on() callbacks. As other subsystems need this information too, move it to init/main.c and make it generally available. While at it, toggle the boolean to early_boot_irqs_disabled instead of enabled so that it can be initialized with %false and %true indicates the exceptional condition. Signed-off-by: Tejun Heo Acked-by: Peter Zijlstra Acked-by: Pekka Enberg Cc: Linus Torvalds LKML-Reference: <20110120110635.GB6036@htj.dyndns.org> Signed-off-by: Ingo Molnar --- include/linux/kernel.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 5a9d9059520b..d07d8057e440 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -243,6 +243,8 @@ extern int test_taint(unsigned flag); extern unsigned long get_taint(void); extern int root_mountflags; +extern bool early_boot_irqs_disabled; + /* Values used for system_state */ extern enum system_states { SYSTEM_BOOTING, -- cgit v1.2.2 From 7ef88ad561457c0346355dfd1f53e503ddfde719 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 24 Jan 2011 14:45:10 -0600 Subject: BUILD_BUG_ON: make it handle more cases BUILD_BUG_ON used to use the optimizer to do code elimination or fail at link time; it was changed to first the size of a negative array (a nicer compile time error), then (in 8c87df457cb58fe75b9b893007917cf8095660a0) to a bitfield. This forced us to change some non-constant cases to MAYBE_BUILD_BUG_ON(); as Jan points out in that commit, it didn't work as intended anyway. bitfields: needs a literal constant at parse time, and can't be put under "if (__builtin_constant_p(x))" for example. negative array: can handle anything, but if the compiler can't tell it's a constant, silently has no effect. link time: breaks link if the compiler can't determine the value, but the linker output is not usually as informative as a compiler error. If we use the negative-array-size method *and* the link time trick, we get the ability to use BUILD_BUG_ON() under __builtin_constant_p() branches, and maximal ability for the compiler to detect errors at build time. We also document it thoroughly. Signed-off-by: Rusty Russell Cc: Jan Beulich Acked-by: Hollis Blanchard --- include/linux/kernel.h | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index d07d8057e440..864712f3653d 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -575,12 +575,6 @@ struct sysinfo { char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */ }; -/* Force a compilation error if condition is true */ -#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition)) - -/* Force a compilation error if condition is constant and true */ -#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)])) - /* Force a compilation error if a constant expression is not a power of 2 */ #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \ BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) @@ -592,6 +586,33 @@ struct sysinfo { #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); })) #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); })) +/** + * BUILD_BUG_ON - break compile if a condition is true. + * @cond: the condition which the compiler should know is false. + * + * If you have some code which relies on certain constants being equal, or + * other compile-time-evaluated condition, you should use BUILD_BUG_ON to + * detect if someone changes it. + * + * The implementation uses gcc's reluctance to create a negative array, but + * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments + * to inline functions). So as a fallback we use the optimizer; if it can't + * prove the condition is false, it will cause a link error on the undefined + * "__build_bug_on_failed". This error message can be harder to track down + * though, hence the two different methods. + */ +#ifndef __OPTIMIZE__ +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) +#else +extern int __build_bug_on_failed; +#define BUILD_BUG_ON(condition) \ + do { \ + ((void)sizeof(char[1 - 2*!!(condition)])); \ + if (condition) __build_bug_on_failed = 1; \ + } while(0) +#endif +#define MAYBE_BUILD_BUG_ON(condition) BUILD_BUG_ON(condition) + /* Trap pasters of __FUNCTION__ at compile-time */ #define __FUNCTION__ (__func__) -- cgit v1.2.2 From 1765e3a4933ea0870fabd755feffc5473c4363ce Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 24 Jan 2011 14:45:10 -0600 Subject: Remove MAYBE_BUILD_BUG_ON Now BUILD_BUG_ON() can handle optimizable constants, we don't need MAYBE_BUILD_BUG_ON any more. Signed-off-by: Rusty Russell --- include/linux/kernel.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 864712f3653d..e2f4d6af2125 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -611,7 +611,6 @@ extern int __build_bug_on_failed; if (condition) __build_bug_on_failed = 1; \ } while(0) #endif -#define MAYBE_BUILD_BUG_ON(condition) BUILD_BUG_ON(condition) /* Trap pasters of __FUNCTION__ at compile-time */ #define __FUNCTION__ (__func__) -- cgit v1.2.2 From ffbbf2da9e578dc7b7ae4f945412c4b74f54b20e Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Mon, 31 Jan 2011 09:29:14 -0800 Subject: kernel.h: fix kernel-doc warning Fix kernel-doc warning in kernel.h from commit 7ef88ad56145 ("BUILD_BUG_ON: make it handle more cases"): Warning(include/linux/kernel.h:605): No description found for parameter 'condition' Warning(include/linux/kernel.h:605): Excess function parameter 'cond' description in 'BUILD_BUG_ON' Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index e2f4d6af2125..2fe6e84894a4 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -588,7 +588,7 @@ struct sysinfo { /** * BUILD_BUG_ON - break compile if a condition is true. - * @cond: the condition which the compiler should know is false. + * @condition: the condition which the compiler should know is false. * * If you have some code which relies on certain constants being equal, or * other compile-time-evaluated condition, you should use BUILD_BUG_ON to -- cgit v1.2.2