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As a replacement for the wait_on_atomic_t() API provide the wait_var_event() API. The wait_var_event() API is based on the very same hashed-waitqueue idea, but doesn't care about the type (atomic_t) or the specific condition (atomic_read() == 0). IOW. it's much more widely applicable/flexible. It shares all the benefits/disadvantages of a hashed-waitqueue approach with the existing wait_on_atomic_t/wait_on_bit() APIs. The API is modeled after the existing wait_event() API, but instead of taking a wait_queue_head, it takes an address. This addresses is hashed to obtain a wait_queue_head from the bit_wait_table. Similar to the wait_event() API, it takes a condition expression as second argument and will wait until this expression becomes true. The following are (mostly) identical replacements: wait_on_atomic_t(&my_atomic, atomic_t_wait, TASK_UNINTERRUPTIBLE); wake_up_atomic_t(&my_atomic); wait_var_event(&my_atomic, !atomic_read(&my_atomic)); wake_up_var(&my_atomic); The only difference is that wake_up_var() is an unconditional wakeup and doesn't check the previously hard-coded (atomic_read() == 0) condition here. This is of little concequence, since most callers are already conditional on atomic_dec_and_test() and the ones that are not, are trivial to make so. Tested-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: David Howells <dhowells@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.