mirror of https://github.com/xzeldon/htop.git
Avoid zombie processes on signal races
The system curses library can handle terminal size changes with SIGWINCH without asking system calls to restart, which effectively stops system calls with -1 and EINTR. An example is ncurses on Linux systems. One of these system calls is waitpid. While waiting for the lsof child to complete, a badly timed SIGWINCH can interrupt the waitpid call, effectively never clearing the state of the child, keeping the zombie until htop exits. Proof of Concept: #include <unistd.h> int main(void) { close(1); close(2); sleep(5); return 0; } Compile this as a replacement "lsof" and put it into your path. Make sure that it's called instead of the real lsof. Press "l" to list open files and resize your terminal within the next 5 seconds. You will see that a zombie process is kept by htop when the timeout finishes.
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@ -9,6 +9,7 @@ in the source distribution for its full text.
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#include "OpenFilesScreen.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <inttypes.h>
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#include <stdio.h>
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@ -197,10 +198,11 @@ static OpenFiles_ProcessData* OpenFilesScreen_getProcessData(pid_t pid) {
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fclose(fd);
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int wstatus;
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if (waitpid(child, &wstatus, 0) == -1) {
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pdata->error = 1;
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return pdata;
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}
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while (waitpid(child, &wstatus, 0) == -1)
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if (errno != EINTR) {
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pdata->error = 1;
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return pdata;
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}
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if (!WIFEXITED(wstatus)) {
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pdata->error = 1;
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@ -10,6 +10,7 @@ in the source distribution for its full text.
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#include "TraceScreen.h"
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdbool.h>
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@ -47,7 +48,9 @@ void TraceScreen_delete(Object* cast) {
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TraceScreen* this = (TraceScreen*) cast;
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if (this->child > 0) {
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kill(this->child, SIGTERM);
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waitpid(this->child, NULL, 0);
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while (waitpid(this->child, NULL, 0) == -1)
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if (errno != EINTR)
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break;
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}
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if (this->strace) {
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