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authorHeiher <r@hev.cc>2019-12-04 16:52:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-12-04 19:44:13 -0800
commit339ddb53d373baee6e7946aec17c739c4924d6d9 (patch)
treea4e439109c84284fc7ecafd87c5e60e16efa7d9d /tools/testing/selftests/Makefile
parentepoll: simplify ep_poll_safewake() for CONFIG_DEBUG_LOCK_ALLOC (diff)
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fs/epoll: remove unnecessary wakeups of nested epoll
Take the case where we have: t0 | (ew) e0 | (et) e1 | (lt) s0 t0: thread 0 e0: epoll fd 0 e1: epoll fd 1 s0: socket fd 0 ew: epoll_wait et: edge-trigger lt: level-trigger We remove unnecessary wakeups to prevent the nested epoll that working in edge- triggered mode to waking up continuously. Test code: #include <unistd.h> #include <sys/epoll.h> #include <sys/socket.h> int main(int argc, char *argv[]) { int sfd[2]; int efd[2]; struct epoll_event e; if (socketpair(AF_UNIX, SOCK_STREAM, 0, sfd) < 0) goto out; efd[0] = epoll_create(1); if (efd[0] < 0) goto out; efd[1] = epoll_create(1); if (efd[1] < 0) goto out; e.events = EPOLLIN; if (epoll_ctl(efd[1], EPOLL_CTL_ADD, sfd[0], &e) < 0) goto out; e.events = EPOLLIN | EPOLLET; if (epoll_ctl(efd[0], EPOLL_CTL_ADD, efd[1], &e) < 0) goto out; if (write(sfd[1], "w", 1) != 1) goto out; if (epoll_wait(efd[0], &e, 1, 0) != 1) goto out; if (epoll_wait(efd[0], &e, 1, 0) != 0) goto out; close(efd[0]); close(efd[1]); close(sfd[0]); close(sfd[1]); return 0; out: return -1; } More tests: https://github.com/heiher/epoll-wakeup Link: http://lkml.kernel.org/r/20191009060516.3577-1-r@hev.cc Signed-off-by: hev <r@hev.cc> Reviewed-by: Roman Penyaev <rpenyaev@suse.de> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Eric Wong <e@80x24.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Sridhar Samudrala <sridhar.samudrala@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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