Craig Tiller
8 years ago
parent
557c88c3ac
commit
376887d213
25 changed files with 363 additions and 210 deletions
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/*
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* |
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* Copyright 2017, Google Inc. |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions are |
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* met: |
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* |
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* * Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* * Redistributions in binary form must reproduce the above |
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* copyright notice, this list of conditions and the following disclaimer |
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* in the documentation and/or other materials provided with the |
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* distribution. |
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* * Neither the name of Google Inc. nor the names of its |
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* contributors may be used to endorse or promote products derived from |
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* this software without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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* |
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*/ |
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#include "src/core/lib/iomgr/lockfree_event.h" |
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#include <grpc/support/log.h> |
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/* 'state' holds the to call when the fd is readable or writable respectively.
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It can contain one of the following values: |
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CLOSURE_READY : The fd has an I/O event of interest but there is no |
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closure yet to execute |
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CLOSURE_NOT_READY : The fd has no I/O event of interest |
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closure ptr : The closure to be executed when the fd has an I/O |
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event of interest |
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shutdown_error | FD_SHUTDOWN_BIT : |
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'shutdown_error' field ORed with FD_SHUTDOWN_BIT. |
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This indicates that the fd is shutdown. Since all |
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memory allocations are word-aligned, the lower two |
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bits of the shutdown_error pointer are always 0. So |
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it is safe to OR these with FD_SHUTDOWN_BIT |
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Valid state transitions: |
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<closure ptr> <-----3------ CLOSURE_NOT_READY ----1----> CLOSURE_READY |
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| | ^ | ^ | | |
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| | | | | | | |
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| +--------------4----------+ 6 +---------2---------------+ | |
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| | | |
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| v | |
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+-----5-------> [shutdown_error | FD_SHUTDOWN_BIT] <----7---------+ |
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For 1, 4 : See grpc_lfev_set_ready() function |
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For 2, 3 : See grpc_lfev_notify_on() function |
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For 5,6,7: See grpc_lfev_set_shutdown() function */ |
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#define CLOSURE_NOT_READY ((gpr_atm)0) |
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#define CLOSURE_READY ((gpr_atm)2) |
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#define FD_SHUTDOWN_BIT 1 |
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void grpc_lfev_init(gpr_atm *state) { |
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gpr_atm_no_barrier_store(state, CLOSURE_NOT_READY); |
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} |
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void grpc_lfev_notify_on(grpc_exec_ctx *exec_ctx, gpr_atm *state, |
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grpc_closure *closure) { |
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while (true) { |
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gpr_atm curr = gpr_atm_no_barrier_load(state); |
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switch (curr) { |
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case CLOSURE_NOT_READY: { |
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/* CLOSURE_NOT_READY -> <closure>.
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We're guaranteed by API that there's an acquire barrier before here, |
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so there's no need to double-dip and this can be a release-only. |
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The release itself pairs with the acquire half of a set_ready full |
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barrier. */ |
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if (gpr_atm_rel_cas(state, CLOSURE_NOT_READY, (gpr_atm)closure)) { |
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return; /* Successful. Return */ |
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} |
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break; /* retry */ |
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} |
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case CLOSURE_READY: { |
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/* Change the state to CLOSURE_NOT_READY. Schedule the closure if
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successful. If not, the state most likely transitioned to shutdown. |
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We should retry. |
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This can be a no-barrier cas since the state is being transitioned to |
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CLOSURE_NOT_READY; set_ready and set_shutdown do not schedule any |
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closure when transitioning out of CLOSURE_NO_READY state (i.e there |
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is no other code that needs to 'happen-after' this) */ |
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if (gpr_atm_no_barrier_cas(state, CLOSURE_READY, CLOSURE_NOT_READY)) { |
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grpc_closure_sched(exec_ctx, closure, GRPC_ERROR_NONE); |
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return; /* Successful. Return */ |
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} |
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break; /* retry */ |
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} |
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default: { |
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/* 'curr' is either a closure or the fd is shutdown(in which case 'curr'
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contains a pointer to the shutdown-error). If the fd is shutdown, |
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schedule the closure with the shutdown error */ |
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if ((curr & FD_SHUTDOWN_BIT) > 0) { |
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grpc_error *shutdown_err = (grpc_error *)(curr & ~FD_SHUTDOWN_BIT); |
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grpc_closure_sched(exec_ctx, closure, |
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GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING( |
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"FD Shutdown", &shutdown_err, 1)); |
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return; |
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} |
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/* There is already a closure!. This indicates a bug in the code */ |
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gpr_log(GPR_ERROR, |
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"notify_on called with a previous callback still pending"); |
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abort(); |
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} |
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} |
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} |
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GPR_UNREACHABLE_CODE(return ); |
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} |
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bool grpc_lfev_set_shutdown(grpc_exec_ctx *exec_ctx, gpr_atm *state, |
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grpc_error *shutdown_err) { |
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gpr_atm new_state = (gpr_atm)shutdown_err | FD_SHUTDOWN_BIT; |
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while (true) { |
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gpr_atm curr = gpr_atm_no_barrier_load(state); |
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switch (curr) { |
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case CLOSURE_READY: |
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case CLOSURE_NOT_READY: |
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/* Need a full barrier here so that the initial load in notify_on
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doesn't need a barrier */ |
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if (gpr_atm_full_cas(state, curr, new_state)) { |
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return true; /* early out */ |
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} |
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break; /* retry */ |
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default: { |
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/* 'curr' is either a closure or the fd is already shutdown */ |
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/* If fd is already shutdown, we are done */ |
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if ((curr & FD_SHUTDOWN_BIT) > 0) { |
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GRPC_ERROR_UNREF(shutdown_err); |
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return false; |
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} |
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/* Fd is not shutdown. Schedule the closure and move the state to
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shutdown state. |
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Needs an acquire to pair with setting the closure (and get a |
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happens-after on that edge), and a release to pair with anything |
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loading the shutdown state. */ |
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if (gpr_atm_full_cas(state, curr, new_state)) { |
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grpc_closure_sched(exec_ctx, (grpc_closure *)curr, |
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GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING( |
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"FD Shutdown", &shutdown_err, 1)); |
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return true; |
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} |
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/* 'curr' was a closure but now changed to a different state. We will
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have to retry */ |
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break; |
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} |
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} |
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} |
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GPR_UNREACHABLE_CODE(return false); |
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} |
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void grpc_lfev_set_ready(grpc_exec_ctx *exec_ctx, gpr_atm *state) { |
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while (true) { |
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gpr_atm curr = gpr_atm_no_barrier_load(state); |
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switch (curr) { |
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case CLOSURE_READY: { |
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/* Already ready. We are done here */ |
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return; |
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} |
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case CLOSURE_NOT_READY: { |
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/* No barrier required as we're transitioning to a state that does not
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involve a closure */ |
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if (gpr_atm_no_barrier_cas(state, CLOSURE_NOT_READY, CLOSURE_READY)) { |
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return; /* early out */ |
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} |
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break; /* retry */ |
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} |
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default: { |
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/* 'curr' is either a closure or the fd is shutdown */ |
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if ((curr & FD_SHUTDOWN_BIT) > 0) { |
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/* The fd is shutdown. Do nothing */ |
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return; |
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} |
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/* Full cas: acquire pairs with this cas' release in the event of a
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spurious set_ready; release pairs with this or the acquire in |
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notify_on (or set_shutdown) */ |
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else if (gpr_atm_full_cas(state, curr, CLOSURE_NOT_READY)) { |
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grpc_closure_sched(exec_ctx, (grpc_closure *)curr, GRPC_ERROR_NONE); |
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return; |
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} |
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/* else the state changed again (only possible by either a racing
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set_ready or set_shutdown functions. In both these cases, the closure |
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would have been scheduled for execution. So we are done here */ |
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return; |
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} |
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} |
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} |
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} |
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@ -0,0 +1,52 @@ |
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/*
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* |
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* Copyright 2017, Google Inc. |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions are |
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* met: |
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* |
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* * Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* * Redistributions in binary form must reproduce the above |
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* copyright notice, this list of conditions and the following disclaimer |
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* in the documentation and/or other materials provided with the |
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* distribution. |
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* * Neither the name of Google Inc. nor the names of its |
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* contributors may be used to endorse or promote products derived from |
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* this software without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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* |
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*/ |
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#ifndef GRPC_CORE_LIB_IOMGR_LOCKFREE_EVENT_H |
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#define GRPC_CORE_LIB_IOMGR_LOCKFREE_EVENT_H |
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/* Lock free event notification for file descriptors */ |
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#include "src/core/lib/iomgr/exec_ctx.h" |
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void grpc_lfev_init(gpr_atm *state); |
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void grpc_lfev_destroy(gpr_atm *state); |
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bool grpc_lfev_is_shutdown(gpr_atm *state); |
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void grpc_lfev_notify_on(grpc_exec_ctx *exec_ctx, gpr_atm *state, |
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grpc_closure *closure); |
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/* Returns true on first successful shutdown */ |
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bool grpc_lfev_set_shutdown(grpc_exec_ctx *exec_ctx, gpr_atm *state, |
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grpc_error *shutdown_err); |
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void grpc_lfev_set_ready(grpc_exec_ctx *exec_ctx, gpr_atm *state); |
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#endif /* GRPC_CORE_LIB_IOMGR_LOCKFREE_EVENT_H */ |
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