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51 lines
1.3 KiB
C++
51 lines
1.3 KiB
C++
// Many build systems attempt to invoke as many linker processes as there
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// are cores, based on the assumption that the linker is single-threaded.
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// However, since mold is multi-threaded, such build systems' behavior is
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// not beneficial and just increases the overall peak memory usage.
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// On machines with limited memory, this could lead to an out-of-memory
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// error.
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//
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// This file implements a feature that limits the number of concurrent
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// mold processes to just 1 for each user. It is intended to be used as
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// `MOLD_JOBS=1 ninja` or `MOLD_JOBS=1 make -j$(nproc)`.
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#include "common.h"
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#include <fcntl.h>
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#include <pwd.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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namespace mold {
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static int lock_fd = -1;
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void acquire_global_lock() {
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char *jobs = getenv("MOLD_JOBS");
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if (!jobs || jobs != "1"s)
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return;
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std::string path;
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if (char *dir = getenv("XDG_RUNTIME_DIR"))
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path = dir + "/mold-lock"s;
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else
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path = "/tmp/mold-lock-"s + getpwuid(getuid())->pw_name;
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int fd = open(path.c_str(), O_WRONLY | O_CREAT | O_CLOEXEC, 0600);
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if (fd == -1)
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return;
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if (lockf(fd, F_LOCK, 0) == -1)
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return;
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lock_fd = fd;
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}
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void release_global_lock() {
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if (lock_fd != -1)
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close(lock_fd);
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}
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} // namespace mold
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