JehanneOS/newlib
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

minor wording changes

Browse Source
This commit is contained in:
Christopher Faylor 2001-09-05 20:12:38 +00:00
parent 6da0fb340e
commit b6077b89be
1 changed files with 16 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
winsup/cygwin/how-signals-work.txt
View File

@ -27,9 +27,10 @@ This array is located in the 'sigtodo' array in the procinfo class.
The signal thread uses the InterlockedDecrement function to atomically The signal thread uses the InterlockedDecrement function to atomically
inspect elements of the array. If one one of the elements of the array inspect elements of the array. If one one of the elements of the array
is non-zero, then cygwin checks to see if the user has blocked the signal is non-zero, then cygwin checks to see if the user has blocked the
by inspecting the process signal mask. If the signal is blocked, then signal by inspecting the process signal mask. If the signal is blocked,
the array is reincremented and the next element is checked. then the current array element is reincremented and the next element is
checked.
If the signal is not blocked, then the function "sig_handle" is called If the signal is not blocked, then the function "sig_handle" is called
with the signal number as an argument. This is a fairly straightforward with the signal number as an argument. This is a fairly straightforward
@ -53,13 +54,16 @@ signal processing is in setup_handler.
setup_handler has a "simple" task. It tries to stop the appropriate setup_handler has a "simple" task. It tries to stop the appropriate
thread and redirect its execution to the signal handler function. thread and redirect its execution to the signal handler function.
Currently, the "appropriate thread" is only the main thread. Currently, the "appropriate thread" is only the main thread. Someday
we'll have to change this to allow cygwin to interrupt other user
threads.
To accomplish this, setup_handler first inspects the static sigsave To accomplish its task, setup_handler first inspects the static sigsave
structure. This structure contains information on any not-yet-handled structure. This structure contains information on any not-yet-handled
signals that may have been set up by a previous call to setup_handler signals that may have been set up by a previous call to setup_handler
but not yet dispatched in the main thread. If the sigsave structure but not yet dispatched in the main thread. If the sigsave structure
seems to be "active", then a "pending" flag is set (see below). seems to be "active", then a "pending" flag is set (see below) and the
function returns. Otherwise processing continues.
After determining that sigsave is available, setup_handler will take After determining that sigsave is available, setup_handler will take
one of two routes, depending on whether the main thread is executing one of two routes, depending on whether the main thread is executing
@ -85,11 +89,11 @@ caller. Rather, it returns to sigdelayed.
The sigdelayed function saves a lot of state on the stack and sets the The sigdelayed function saves a lot of state on the stack and sets the
signal mask as appropriate for POSIX. It uses information from the signal mask as appropriate for POSIX. It uses information from the
sigsave structure which has been filled in by interrupt_on_return, as sigsave structure which has been filled in by interrupt_on_return, as
called by setup_handler. sigdelayed pushes another "sigreturn" address called by setup_handler. sigdelayed pushes a "call" the function
on the stack. This will be the return address seen by the signal "sigreturn" on the stack. This will be the return address seen by the
handler. After setting up the return value, modifying the signal mask, signal handler. After setting up the return value, modifying the signal
and saving other information on the stack, sigreturn clears the sigsave mask, and saving other information on the stack, sigreturn clears the
structure (so that setup_handler can use it) and jumps to the signal sigsave structure (so that setup_handler can use it) and jumps to the
handler function. signal handler function.