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Processing (Linux): fix potential hang when reading large buffer

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`write` in child process blocks when the pipe is full. However because we are `waitpid`ing, we don't read the pipe, so that the pipe is never free. Therefore `write` in child process blocks forever and `waitpid` hangs.

Fix #493
This commit is contained in:
李通洲
2023-07-11 11:10:10 +08:00
parent 7dae59ee92
commit ced2347829
1 changed files with 21 additions and 57 deletions
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src/common/processing_linux.c
+21 -57
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@@ -5,55 +5,8 @@
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <signal.h>
#ifdef __linux__
#include <sys/syscall.h>
#include <poll.h>
#endif
int waitpid_timeout(pid_t pid, int* status)
{
if (instance.config.processingTimeout <= 0)
return waitpid(pid, status, 0);
uint32_t timeout = (uint32_t) instance.config.processingTimeout;
#if defined(__linux__) && defined(SYS_pidfd_open) // musl don't define SYS_pidfd_open
FF_AUTO_CLOSE_FD int pidfd = (int) syscall(SYS_pidfd_open, pid, 0);
if (pidfd >= 0)
{
int res = poll(&(struct pollfd) { .events = POLLIN, .fd = pidfd }, 1, (int) timeout);
if (res > 0)
return (int) waitpid(pid, status, WNOHANG);
else if (res == 0)
{
kill(pid, SIGTERM);
return -62; // -ETIME
}
return -1;
}
#endif
uint64_t start = ffTimeGetTick();
while (true)
{
int res = (int) waitpid(pid, status, WNOHANG);
if (res != 0)
return res;
if (ffTimeGetTick() - start < timeout)
ffTimeSleep(timeout / 10);
else
{
kill(pid, SIGTERM);
return -62; // -ETIME
}
}
}
#include <poll.h>
const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool useStdErr)
{
@@ -81,16 +34,27 @@ const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool use
close(pipes[1]);
int FF_AUTO_CLOSE_FD childPipeFd = pipes[0];
int status = -1;
if(waitpid_timeout(childPid, &status) < 0)
return "waitpid(childPid, &status) failed";
if (!WIFEXITED(status))
return "WIFEXITED(status) == false";
if(WEXITSTATUS(status) == 901)
return "WEXITSTATUS(status) == 901 ( execvp failed )";
if (instance.config.processingTimeout >= 0)
{
struct pollfd pollfd = { childPipeFd, POLLIN, 0 };
if (poll(&pollfd, 1, (int) instance.config.processingTimeout) == 0)
{
kill(childPid, SIGTERM);
return "poll(&pollfd, 1, (int) instance.config.processingTimeout) timeout";
}
else if (pollfd.revents & POLLERR)
{
kill(childPid, SIGTERM);
return "poll(&pollfd, 1, (int) instance.config.processingTimeout) error";
}
else if (pollfd.revents & POLLHUP)
{
return "Child process closed its end (nothing to read)";
}
}
// Note that we only know we have something to read here
// However the child process may still block later
if(!ffAppendFDBuffer(childPipeFd, buffer))
return "ffAppendFDBuffer(childPipeFd, buffer) failed";