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authorPeter Zijlstra <peterz@infradead.org>2019-03-19 13:18:56 +0100
committerIngo Molnar <mingo@kernel.org>2019-04-03 11:42:33 +0200
commita1247d06d01045d7ab2882a9c074fbf21137c690 (patch)
treede30aa6f8d6a1f35a5bf17932d0ea5fe1c598c62 /arch/s390
parentMerge branch 'work.aio' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs (diff)
downloadlinux-dev-a1247d06d01045d7ab2882a9c074fbf21137c690.tar.xz
linux-dev-a1247d06d01045d7ab2882a9c074fbf21137c690.zip
locking/static_key: Fix false positive warnings on concurrent dec/inc
Even though the atomic_dec_and_mutex_lock() in __static_key_slow_dec_cpuslocked() can never see a negative value in key->enabled the subsequent sanity check is re-reading key->enabled, which may have been set to -1 in the meantime by static_key_slow_inc_cpuslocked(). CPU A CPU B __static_key_slow_dec_cpuslocked(): static_key_slow_inc_cpuslocked(): # enabled = 1 atomic_dec_and_mutex_lock() # enabled = 0 atomic_read() == 0 atomic_set(-1) # enabled = -1 val = atomic_read() # Oops - val == -1! The test case is TCP's clean_acked_data_enable() / clean_acked_data_disable() as tickled by KTLS (net/ktls). Suggested-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com> Tested-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: ard.biesheuvel@linaro.org Cc: oss-drivers@netronome.com Cc: pbonzini@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/s390')
0 files changed, 0 insertions, 0 deletions