summaryrefslogtreecommitdiff
path: root/sound/pci/maestro3.c
diff options
context:
space:
mode:
authorIngo Molnar <mingo@kernel.org>2024-12-06 10:19:31 +0100
committerIngo Molnar <mingo@kernel.org>2024-12-07 11:15:14 +0100
commitb4d83c8323b0c4a899a996fed919cfe10720d289 (patch)
tree02e6a9868b58aaec73e711711dc9de26df30e1fe /sound/pci/maestro3.c
parent0302d2fd6efb0c386e521df0134eb2679a9a138f (diff)
headers/cleanup.h: Remove the if_not_guard() facility
Linus noticed that the new if_not_guard() definition is fragile: "This macro generates actively wrong code if it happens to be inside an if-statement or a loop without a block. IOW, code like this: for (iterate-over-something) if_not_guard(a) return -BUSY; looks like will build fine, but will generate completely incorrect code." The reason is that the __if_not_guard() macro is multi-statement, so while most kernel developers expect macros to be simple or at least compound statements - but for __if_not_guard() it is not so: #define __if_not_guard(_name, _id, args...) \ BUILD_BUG_ON(!__is_cond_ptr(_name)); \ CLASS(_name, _id)(args); \ if (!__guard_ptr(_name)(&_id)) To add insult to injury, the placement of the BUILD_BUG_ON() line makes the macro appear to compile fine, but it will generate incorrect code as Linus reported, for example if used within iteration or conditional statements that will use the first statement of a macro as a loop body or conditional statement body. [ I'd also like to note that the original submission by David Lechner did not contain the BUILD_BUG_ON() line, so it was safer than what we ended up committing. Mea culpa. ] It doesn't appear to be possible to turn this macro into a robust single or compound statement that could be used in single statements, due to the necessity to define an auto scope variable with an open scope and the necessity of it having to expand to a partial 'if' statement with no body. Instead of trying to work around this fragility, just remove the construct before it gets used. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: David Lechner <dlechner@baylibre.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/Z1LBnX9TpZLR5Dkf@gmail.com
Diffstat (limited to 'sound/pci/maestro3.c')
0 files changed, 0 insertions, 0 deletions