mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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720abae3d6
Make struct callback_head aligned to size of pointer. On most architectures it happens naturally due ABI requirements, but some architectures (like CRIS) have weird ABI and we need to ask it explicitly. The alignment is required to guarantee that bits 0 and 1 of @next will be clear under normal conditions -- as long as we use call_rcu(), call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback. This guarantee is important for few reasons: - future call_rcu_lazy() will make use of lower bits in the pointer; - the structure shares storage spacer in struct page with @compound_head, which encode PageTail() in bit 0. The guarantee is needed to avoid false-positive PageTail(). False postive PageTail() caused crash on crisv32[1]. It happend due misaligned task_struct->rcu, which was byte-aligned. [1] http://lkml.kernel.org/r/55FAEA67.9000102@roeck-us.net Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Guenter Roeck <linux@roeck-us.net> Tested-by: Guenter Roeck <linux@roeck-us.net> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Mikael Starvik <starvik@axis.com> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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